content: /*
   * Copyright (C) 2006 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.text.format;
  
  import android.annotation.UnsupportedAppUsage;
  import android.content.Context;
  import android.content.res.Configuration;
  import android.content.res.Resources;
  import android.icu.text.MeasureFormat;
  import android.icu.text.MeasureFormat.FormatWidth;
  import android.icu.util.Measure;
  import android.icu.util.MeasureUnit;
  
  import com.android.internal.R;
  
  import libcore.icu.DateIntervalFormat;
  import libcore.icu.LocaleData;
  import libcore.icu.RelativeDateTimeFormatter;
  
  import java.io.IOException;
  import java.util.Calendar;
  import java.util.Date;
  import java.util.Formatter;
  import java.util.GregorianCalendar;
  import java.util.Locale;
  import java.util.TimeZone;
  
  /**
   * This class contains various date-related utilities for creating text for things like
   * elapsed time and date ranges, strings for days of the week and months, and AM/PM text etc.
   */
  public class DateUtils
  {
      private static final Object sLock = new Object();
      private static Configuration sLastConfig;
      private static String sElapsedFormatMMSS;
      private static String sElapsedFormatHMMSS;
  
      public static final long SECOND_IN_MILLIS = 1000;
      public static final long MINUTE_IN_MILLIS = SECOND_IN_MILLIS * 60;
      public static final long HOUR_IN_MILLIS = MINUTE_IN_MILLIS * 60;
      public static final long DAY_IN_MILLIS = HOUR_IN_MILLIS * 24;
      public static final long WEEK_IN_MILLIS = DAY_IN_MILLIS * 7;
      /**
       * This constant is actually the length of 364 days, not of a year!
       */
      public static final long YEAR_IN_MILLIS = WEEK_IN_MILLIS * 52;
  
      // The following FORMAT_* symbols are used for specifying the format of
      // dates and times in the formatDateRange method.
      public static final int FORMAT_SHOW_TIME = 0x00001;
      public static final int FORMAT_SHOW_WEEKDAY = 0x00002;
      public static final int FORMAT_SHOW_YEAR = 0x00004;
      public static final int FORMAT_NO_YEAR = 0x00008;
      public static final int FORMAT_SHOW_DATE = 0x00010;
      public static final int FORMAT_NO_MONTH_DAY = 0x00020;
      @Deprecated
      public static final int FORMAT_12HOUR = 0x00040;
      @Deprecated
      public static final int FORMAT_24HOUR = 0x00080;
      @Deprecated
      public static final int FORMAT_CAP_AMPM = 0x00100;
      public static final int FORMAT_NO_NOON = 0x00200;
      @Deprecated
      public static final int FORMAT_CAP_NOON = 0x00400;
      public static final int FORMAT_NO_MIDNIGHT = 0x00800;
      @Deprecated
      public static final int FORMAT_CAP_MIDNIGHT = 0x01000;
      /**
       * @deprecated Use
       * {@link #formatDateRange(Context, Formatter, long, long, int, String) formatDateRange}
       * and pass in {@link Time#TIMEZONE_UTC Time.TIMEZONE_UTC} for the timeZone instead.
       */
      @Deprecated
      public static final int FORMAT_UTC = 0x02000;
      public static final int FORMAT_ABBREV_TIME = 0x04000;
      public static final int FORMAT_ABBREV_WEEKDAY = 0x08000;
      public static final int FORMAT_ABBREV_MONTH = 0x10000;
      public static final int FORMAT_NUMERIC_DATE = 0x20000;
      public static final int FORMAT_ABBREV_RELATIVE = 0x40000;
      public static final int FORMAT_ABBREV_ALL = 0x80000;
      @Deprecated
      public static final int FORMAT_CAP_NOON_MIDNIGHT = (FORMAT_CAP_NOON | FORMAT_CAP_MIDNIGHT);
      @Deprecated
      public static final int FORMAT_NO_NOON_MIDNIGHT = (FORMAT_NO_NOON | FORMAT_NO_MIDNIGHT);
  
      // Date and time format strings that are constant and don't need to be
      // translated.
      /**
       * This is not actually the preferred 24-hour date format in all locales.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final String HOUR_MINUTE_24 = "%H:%M";
      public static final String MONTH_FORMAT = "%B";
      /**
       * This is not actually a useful month name in all locales.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final String ABBREV_MONTH_FORMAT = "%b";
      public static final String NUMERIC_MONTH_FORMAT = "%m";
      public static final String MONTH_DAY_FORMAT = "%-d";
      public static final String YEAR_FORMAT = "%Y";
      public static final String YEAR_FORMAT_TWO_DIGITS = "%g";
      public static final String WEEKDAY_FORMAT = "%A";
      public static final String ABBREV_WEEKDAY_FORMAT = "%a";
  
      /** @deprecated Do not use. */
      @Deprecated
      public static final int[] sameYearTable = null;
  
      /** @deprecated Do not use. */
      @Deprecated
      public static final int[] sameMonthTable = null;
  
      /**
       * Request the full spelled-out name. For use with the 'abbrev' parameter of
       * {@link #getDayOfWeekString} and {@link #getMonthString}.
       *
       * @more <p>
       *       e.g. "Sunday" or "January"
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final int LENGTH_LONG = 10;
  
      /**
       * Request an abbreviated version of the name. For use with the 'abbrev'
       * parameter of {@link #getDayOfWeekString} and {@link #getMonthString}.
       *
       * @more <p>
       *       e.g. "Sun" or "Jan"
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final int LENGTH_MEDIUM = 20;
  
      /**
       * Request a shorter abbreviated version of the name.
       * For use with the 'abbrev' parameter of {@link #getDayOfWeekString} and {@link #getMonthString}.
       * @more
       * <p>e.g. "Su" or "Jan"
       * <p>In most languages, the results returned for LENGTH_SHORT will be the same as
       * the results returned for {@link #LENGTH_MEDIUM}.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final int LENGTH_SHORT = 30;
  
      /**
       * Request an even shorter abbreviated version of the name.
       * Do not use this.  Currently this will always return the same result
       * as {@link #LENGTH_SHORT}.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final int LENGTH_SHORTER = 40;
  
      /**
       * Request an even shorter abbreviated version of the name.
       * For use with the 'abbrev' parameter of {@link #getDayOfWeekString} and {@link #getMonthString}.
       * @more
       * <p>e.g. "S", "T", "T" or "J"
       * <p>In some languages, the results returned for LENGTH_SHORTEST will be the same as
       * the results returned for {@link #LENGTH_SHORT}.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static final int LENGTH_SHORTEST = 50;
  
      /**
       * Return a string for the day of the week.
       * @param dayOfWeek One of {@link Calendar#SUNDAY Calendar.SUNDAY},
       *               {@link Calendar#MONDAY Calendar.MONDAY}, etc.
       * @param abbrev One of {@link #LENGTH_LONG}, {@link #LENGTH_SHORT},
       *               {@link #LENGTH_MEDIUM}, or {@link #LENGTH_SHORTEST}.
       *               Note that in most languages, {@link #LENGTH_SHORT}
       *               will return the same as {@link #LENGTH_MEDIUM}.
       *               Undefined lengths will return {@link #LENGTH_MEDIUM}
       *               but may return something different in the future.
       * @throws IndexOutOfBoundsException if the dayOfWeek is out of bounds.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static String getDayOfWeekString(int dayOfWeek, int abbrev) {
          LocaleData d = LocaleData.get(Locale.getDefault());
          String[] names;
          switch (abbrev) {
              case LENGTH_LONG:       names = d.longWeekdayNames;  break;
              case LENGTH_MEDIUM:     names = d.shortWeekdayNames; break;
              case LENGTH_SHORT:      names = d.shortWeekdayNames; break; // TODO
              case LENGTH_SHORTER:    names = d.shortWeekdayNames; break; // TODO
              case LENGTH_SHORTEST:   names = d.tinyWeekdayNames;  break;
              default:                names = d.shortWeekdayNames; break;
          }
          return names[dayOfWeek];
      }
  
      /**
       * Return a localized string for AM or PM.
       * @param ampm Either {@link Calendar#AM Calendar.AM} or {@link Calendar#PM Calendar.PM}.
       * @throws IndexOutOfBoundsException if the ampm is out of bounds.
       * @return Localized version of "AM" or "PM".
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static String getAMPMString(int ampm) {
          return LocaleData.get(Locale.getDefault()).amPm[ampm - Calendar.AM];
      }
  
      /**
       * Return a localized string for the month of the year.
       * @param month One of {@link Calendar#JANUARY Calendar.JANUARY},
       *               {@link Calendar#FEBRUARY Calendar.FEBRUARY}, etc.
       * @param abbrev One of {@link #LENGTH_LONG}, {@link #LENGTH_MEDIUM},
       *               or {@link #LENGTH_SHORTEST}.
       *               Undefined lengths will return {@link #LENGTH_MEDIUM}
       *               but may return something different in the future.
       * @return Localized month of the year.
       * @deprecated Use {@link java.text.SimpleDateFormat} instead.
       */
      @Deprecated
      public static String getMonthString(int month, int abbrev) {
          LocaleData d = LocaleData.get(Locale.getDefault());
          String[] names;
          switch (abbrev) {
              case LENGTH_LONG:       names = d.longMonthNames;  break;
              case LENGTH_MEDIUM:     names = d.shortMonthNames; break;
              case LENGTH_SHORT:      names = d.shortMonthNames; break;
              case LENGTH_SHORTER:    names = d.shortMonthNames; break;
              case LENGTH_SHORTEST:   names = d.tinyMonthNames;  break;
              default:                names = d.shortMonthNames; break;
          }
          return names[month];
      }
  
      /**
       * Returns a string describing the elapsed time since startTime.
       * <p>
       * The minimum timespan to report is set to {@link #MINUTE_IN_MILLIS}.
       * @param startTime some time in the past.
       * @return a String object containing the elapsed time.
       * @see #getRelativeTimeSpanString(long, long, long)
       */
      public static CharSequence getRelativeTimeSpanString(long startTime) {
          return getRelativeTimeSpanString(startTime, System.currentTimeMillis(), MINUTE_IN_MILLIS);
      }
  
      /**
       * Returns a string describing 'time' as a time relative to 'now'.
       * <p>
       * Time spans in the past are formatted like "42 minutes ago".
       * Time spans in the future are formatted like "In 42 minutes".
       *
       * @param time the time to describe, in milliseconds
       * @param now the current time in milliseconds
       * @param minResolution the minimum timespan to report. For example, a time 3 seconds in the
       *     past will be reported as "0 minutes ago" if this is set to MINUTE_IN_MILLIS. Pass one of
       *     0, MINUTE_IN_MILLIS, HOUR_IN_MILLIS, DAY_IN_MILLIS, WEEK_IN_MILLIS
       */
      public static CharSequence getRelativeTimeSpanString(long time, long now, long minResolution) {
          int flags = FORMAT_SHOW_DATE | FORMAT_SHOW_YEAR | FORMAT_ABBREV_MONTH;
          return getRelativeTimeSpanString(time, now, minResolution, flags);
      }
  
      /**
       * Returns a string describing 'time' as a time relative to 'now'.
       * <p>
       * Time spans in the past are formatted like "42 minutes ago". Time spans in
       * the future are formatted like "In 42 minutes".
       * <p>
       * Can use {@link #FORMAT_ABBREV_RELATIVE} flag to use abbreviated relative
       * times, like "42 mins ago".
       *
       * @param time the time to describe, in milliseconds
       * @param now the current time in milliseconds
       * @param minResolution the minimum timespan to report. For example, a time
       *            3 seconds in the past will be reported as "0 minutes ago" if
       *            this is set to MINUTE_IN_MILLIS. Pass one of 0,
       *            MINUTE_IN_MILLIS, HOUR_IN_MILLIS, DAY_IN_MILLIS,
       *            WEEK_IN_MILLIS
       * @param flags a bit mask of formatting options, such as
       *            {@link #FORMAT_NUMERIC_DATE} or
       *            {@link #FORMAT_ABBREV_RELATIVE}
       */
      public static CharSequence getRelativeTimeSpanString(long time, long now, long minResolution,
              int flags) {
          return RelativeDateTimeFormatter.getRelativeTimeSpanString(Locale.getDefault(),
                  TimeZone.getDefault(), time, now, minResolution, flags);
      }
  
      /**
       * Return string describing the elapsed time since startTime formatted like
       * "[relative time/date], [time]".
       * <p>
       * Example output strings for the US date format.
       * <ul>
       * <li>3 min. ago, 10:15 AM</li>
       * <li>Yesterday, 12:20 PM</li>
       * <li>Dec 12, 4:12 AM</li>
       * <li>11/14/2007, 8:20 AM</li>
       * </ul>
       *
       * @param time some time in the past.
       * @param minResolution the minimum elapsed time (in milliseconds) to report
       *            when showing relative times. For example, a time 3 seconds in
       *            the past will be reported as "0 minutes ago" if this is set to
       *            {@link #MINUTE_IN_MILLIS}.
       * @param transitionResolution the elapsed time (in milliseconds) at which
       *            to stop reporting relative measurements. Elapsed times greater
       *            than this resolution will default to normal date formatting.
       *            For example, will transition from "7 days ago" to "Dec 12"
       *            when using {@link #WEEK_IN_MILLIS}.
       */
      public static CharSequence getRelativeDateTimeString(Context c, long time, long minResolution,
              long transitionResolution, int flags) {
          // Same reason as in formatDateRange() to explicitly indicate 12- or 24-hour format.
          if ((flags & (FORMAT_SHOW_TIME | FORMAT_12HOUR | FORMAT_24HOUR)) == FORMAT_SHOW_TIME) {
              flags |= DateFormat.is24HourFormat(c) ? FORMAT_24HOUR : FORMAT_12HOUR;
          }
  
          return RelativeDateTimeFormatter.getRelativeDateTimeString(Locale.getDefault(),
                  TimeZone.getDefault(), time, System.currentTimeMillis(), minResolution,
                  transitionResolution, flags);
      }
  
      private static void initFormatStrings() {
          synchronized (sLock) {
              initFormatStringsLocked();
          }
      }
  
      private static void initFormatStringsLocked() {
          Resources r = Resources.getSystem();
          Configuration cfg = r.getConfiguration();
          if (sLastConfig == null || !sLastConfig.equals(cfg)) {
              sLastConfig = cfg;
              sElapsedFormatMMSS = r.getString(com.android.internal.R.string.elapsed_time_short_format_mm_ss);
              sElapsedFormatHMMSS = r.getString(com.android.internal.R.string.elapsed_time_short_format_h_mm_ss);
          }
      }
  
      /**
       * Returns the given duration in a human-friendly format. For example,
       * "4 minutes" or "1 second". Returns only the largest meaningful unit of time,
       * from seconds up to hours.
       *
       * @hide
       */
      @UnsupportedAppUsage
      public static CharSequence formatDuration(long millis) {
          return formatDuration(millis, LENGTH_LONG);
      }
  
      /**
       * Returns the given duration in a human-friendly format. For example,
       * "4 minutes" or "1 second". Returns only the largest meaningful unit of time,
       * from seconds up to hours.
       * <p>
       * You can use abbrev to specify a preference for abbreviations (but note that some
       * locales may not have abbreviations). Use LENGTH_LONG for the full spelling (e.g. "2 hours"),
       * LENGTH_SHORT for the abbreviated spelling if available (e.g. "2 hr"), and LENGTH_SHORTEST for
       * the briefest form available (e.g. "2h").
       * @hide
       */
      @UnsupportedAppUsage
      public static CharSequence formatDuration(long millis, int abbrev) {
          final FormatWidth width;
          switch (abbrev) {
              case LENGTH_LONG:
                  width = FormatWidth.WIDE;
                  break;
              case LENGTH_SHORT:
              case LENGTH_SHORTER:
              case LENGTH_MEDIUM:
                  width = FormatWidth.SHORT;
                  break;
              case LENGTH_SHORTEST:
                  width = FormatWidth.NARROW;
                  break;
              default:
                  width = FormatWidth.WIDE;
          }
          final MeasureFormat formatter = MeasureFormat.getInstance(Locale.getDefault(), width);
          if (millis >= HOUR_IN_MILLIS) {
              final int hours = (int) ((millis + 1800000) / HOUR_IN_MILLIS);
              return formatter.format(new Measure(hours, MeasureUnit.HOUR));
          } else if (millis >= MINUTE_IN_MILLIS) {
              final int minutes = (int) ((millis + 30000) / MINUTE_IN_MILLIS);
              return formatter.format(new Measure(minutes, MeasureUnit.MINUTE));
          } else {
              final int seconds = (int) ((millis + 500) / SECOND_IN_MILLIS);
              return formatter.format(new Measure(seconds, MeasureUnit.SECOND));
          }
      }
  
      /**
       * Formats an elapsed time in the form "MM:SS" or "H:MM:SS"
       * for display on the call-in-progress screen.
       * @param elapsedSeconds the elapsed time in seconds.
       */
      public static String formatElapsedTime(long elapsedSeconds) {
          return formatElapsedTime(null, elapsedSeconds);
      }
  
      /**
       * Formats an elapsed time in a format like "MM:SS" or "H:MM:SS" (using a form
       * suited to the current locale), similar to that used on the call-in-progress
       * screen.
       *
       * @param recycle {@link StringBuilder} to recycle, or null to use a temporary one.
       * @param elapsedSeconds the elapsed time in seconds.
       */
      public static String formatElapsedTime(StringBuilder recycle, long elapsedSeconds) {
          // Break the elapsed seconds into hours, minutes, and seconds.
          long hours = 0;
          long minutes = 0;
          long seconds = 0;
          if (elapsedSeconds >= 3600) {
              hours = elapsedSeconds / 3600;
              elapsedSeconds -= hours * 3600;
          }
          if (elapsedSeconds >= 60) {
              minutes = elapsedSeconds / 60;
              elapsedSeconds -= minutes * 60;
          }
          seconds = elapsedSeconds;
  
          // Create a StringBuilder if we weren't given one to recycle.
          // TODO: if we cared, we could have a thread-local temporary StringBuilder.
          StringBuilder sb = recycle;
          if (sb == null) {
              sb = new StringBuilder(8);
          } else {
              sb.setLength(0);
          }
  
          // Format the broken-down time in a locale-appropriate way.
          // TODO: use icu4c when http://unicode.org/cldr/trac/ticket/3407 is fixed.
          Formatter f = new Formatter(sb, Locale.getDefault());
          initFormatStrings();
          if (hours > 0) {
              return f.format(sElapsedFormatHMMSS, hours, minutes, seconds).toString();
          } else {
              return f.format(sElapsedFormatMMSS, minutes, seconds).toString();
          }
      }
  
      /**
       * Format a date / time such that if the then is on the same day as now, it shows
       * just the time and if it's a different day, it shows just the date.
       *
       * <p>The parameters dateFormat and timeFormat should each be one of
       * {@link java.text.DateFormat#DEFAULT},
       * {@link java.text.DateFormat#FULL},
       * {@link java.text.DateFormat#LONG},
       * {@link java.text.DateFormat#MEDIUM}
       * or
       * {@link java.text.DateFormat#SHORT}
       *
       * @param then the date to format
       * @param now the base time
       * @param dateStyle how to format the date portion.
       * @param timeStyle how to format the time portion.
       */
      public static final CharSequence formatSameDayTime(long then, long now,
              int dateStyle, int timeStyle) {
          Calendar thenCal = new GregorianCalendar();
          thenCal.setTimeInMillis(then);
          Date thenDate = thenCal.getTime();
          Calendar nowCal = new GregorianCalendar();
          nowCal.setTimeInMillis(now);
  
          java.text.DateFormat f;
  
          if (thenCal.get(Calendar.YEAR) == nowCal.get(Calendar.YEAR)
                  && thenCal.get(Calendar.MONTH) == nowCal.get(Calendar.MONTH)
                  && thenCal.get(Calendar.DAY_OF_MONTH) == nowCal.get(Calendar.DAY_OF_MONTH)) {
              f = java.text.DateFormat.getTimeInstance(timeStyle);
          } else {
              f = java.text.DateFormat.getDateInstance(dateStyle);
          }
          return f.format(thenDate);
      }
  
      /**
       * @return true if the supplied when is today else false
       */
      public static boolean isToday(long when) {
          Time time = new Time();
          time.set(when);
  
          int thenYear = time.year;
          int thenMonth = time.month;
          int thenMonthDay = time.monthDay;
  
          time.set(System.currentTimeMillis());
          return (thenYear == time.year)
                  && (thenMonth == time.month)
                  && (thenMonthDay == time.monthDay);
      }
  
      /**
       * Formats a date or a time range according to the local conventions.
       * <p>
       * Note that this is a convenience method. Using it involves creating an
       * internal {@link java.util.Formatter} instance on-the-fly, which is
       * somewhat costly in terms of memory and time. This is probably acceptable
       * if you use the method only rarely, but if you rely on it for formatting a
       * large number of dates, consider creating and reusing your own
       * {@link java.util.Formatter} instance and use the version of
       * {@link #formatDateRange(Context, long, long, int) formatDateRange}
       * that takes a {@link java.util.Formatter}.
       *
       * @param context the context is required only if the time is shown
       * @param startMillis the start time in UTC milliseconds
       * @param endMillis the end time in UTC milliseconds
       * @param flags a bit mask of options See
       * {@link #formatDateRange(Context, Formatter, long, long, int, String) formatDateRange}
       * @return a string containing the formatted date/time range.
       */
      public static String formatDateRange(Context context, long startMillis,
              long endMillis, int flags) {
          Formatter f = new Formatter(new StringBuilder(50), Locale.getDefault());
          return formatDateRange(context, f, startMillis, endMillis, flags).toString();
      }
  
      /**
       * Formats a date or a time range according to the local conventions.
       * <p>
       * Note that this is a convenience method for formatting the date or
       * time range in the local time zone. If you want to specify the time
       * zone please use
       * {@link #formatDateRange(Context, Formatter, long, long, int, String) formatDateRange}.
       *
       * @param context the context is required only if the time is shown
       * @param formatter the Formatter used for formatting the date range.
       * Note: be sure to call setLength(0) on StringBuilder passed to
       * the Formatter constructor unless you want the results to accumulate.
       * @param startMillis the start time in UTC milliseconds
       * @param endMillis the end time in UTC milliseconds
       * @param flags a bit mask of options See
       * {@link #formatDateRange(Context, Formatter, long, long, int, String) formatDateRange}
       * @return a string containing the formatted date/time range.
       */
      public static Formatter formatDateRange(Context context, Formatter formatter, long startMillis,
              long endMillis, int flags) {
          return formatDateRange(context, formatter, startMillis, endMillis, flags, null);
      }
  
      /**
       * Formats a date or a time range according to the local conventions.
       *
       * <p>
       * Example output strings (date formats in these examples are shown using
       * the US date format convention but that may change depending on the
       * local settings):
       * <ul>
       *   <li>10:15am</li>
       *   <li>3:00pm - 4:00pm</li>
       *   <li>3pm - 4pm</li>
       *   <li>3PM - 4PM</li>
       *   <li>08:00 - 17:00</li>
       *   <li>Oct 9</li>
       *   <li>Tue, Oct 9</li>
       *   <li>October 9, 2007</li>
       *   <li>Oct 9 - 10</li>
       *   <li>Oct 9 - 10, 2007</li>
       *   <li>Oct 28 - Nov 3, 2007</li>
       *   <li>Dec 31, 2007 - Jan 1, 2008</li>
       *   <li>Oct 9, 8:00am - Oct 10, 5:00pm</li>
       *   <li>12/31/2007 - 01/01/2008</li>
       * </ul>
       *
       * <p>
       * The flags argument is a bitmask of options from the following list:
       *
       * <ul>
       *   <li>FORMAT_SHOW_TIME</li>
       *   <li>FORMAT_SHOW_WEEKDAY</li>
       *   <li>FORMAT_SHOW_YEAR</li>
       *   <li>FORMAT_SHOW_DATE</li>
       *   <li>FORMAT_NO_MONTH_DAY</li>
       *   <li>FORMAT_12HOUR</li>
       *   <li>FORMAT_24HOUR</li>
       *   <li>FORMAT_CAP_AMPM</li>
       *   <li>FORMAT_NO_NOON</li>
       *   <li>FORMAT_CAP_NOON</li>
       *   <li>FORMAT_NO_MIDNIGHT</li>
       *   <li>FORMAT_CAP_MIDNIGHT</li>
       *   <li>FORMAT_UTC</li>
       *   <li>FORMAT_ABBREV_TIME</li>
       *   <li>FORMAT_ABBREV_WEEKDAY</li>
       *   <li>FORMAT_ABBREV_MONTH</li>
       *   <li>FORMAT_ABBREV_ALL</li>
       *   <li>FORMAT_NUMERIC_DATE</li>
       * </ul>
       *
       * <p>
       * If FORMAT_SHOW_TIME is set, the time is shown as part of the date range.
       * If the start and end time are the same, then just the start time is
       * shown.
       *
       * <p>
       * If FORMAT_SHOW_WEEKDAY is set, then the weekday is shown.
       *
       * <p>
       * If FORMAT_SHOW_YEAR is set, then the year is always shown.
       * If FORMAT_SHOW_YEAR is not set, then the year
       * is shown only if it is different from the current year, or if the start
       * and end dates fall on different years.
       *
       * <p>
       * Normally the date is shown unless the start and end day are the same.
       * If FORMAT_SHOW_DATE is set, then the date is always shown, even for
       * same day ranges.
       *
       * <p>
       * If FORMAT_NO_MONTH_DAY is set, then if the date is shown, just the
       * month name will be shown, not the day of the month.  For example,
       * "January, 2008" instead of "January 6 - 12, 2008".
       *
       * <p>
       * If FORMAT_CAP_AMPM is set and 12-hour time is used, then the "AM"
       * and "PM" are capitalized.  You should not use this flag
       * because in some locales these terms cannot be capitalized, and in
       * many others it doesn't make sense to do so even though it is possible.
       *
       * <p>
       * If FORMAT_NO_NOON is set and 12-hour time is used, then "12pm" is
       * shown instead of "noon".
       *
       * <p>
       * If FORMAT_CAP_NOON is set and 12-hour time is used, then "Noon" is
       * shown instead of "noon".  You should probably not use this flag
       * because in many locales it will not make sense to capitalize
       * the term.
       *
       * <p>
       * If FORMAT_NO_MIDNIGHT is set and 12-hour time is used, then "12am" is
       * shown instead of "midnight".
       *
       * <p>
       * If FORMAT_CAP_MIDNIGHT is set and 12-hour time is used, then "Midnight"
       * is shown instead of "midnight".  You should probably not use this
       * flag because in many locales it will not make sense to capitalize
       * the term.
       *
       * <p>
       * If FORMAT_12HOUR is set and the time is shown, then the time is
       * shown in the 12-hour time format. You should not normally set this.
       * Instead, let the time format be chosen automatically according to the
       * system settings. If both FORMAT_12HOUR and FORMAT_24HOUR are set, then
       * FORMAT_24HOUR takes precedence.
       *
       * <p>
       * If FORMAT_24HOUR is set and the time is shown, then the time is
       * shown in the 24-hour time format. You should not normally set this.
       * Instead, let the time format be chosen automatically according to the
       * system settings. If both FORMAT_12HOUR and FORMAT_24HOUR are set, then
       * FORMAT_24HOUR takes precedence.
       *
       * <p>
       * If FORMAT_UTC is set, then the UTC time zone is used for the start
       * and end milliseconds unless a time zone is specified. If a time zone
       * is specified it will be used regardless of the FORMAT_UTC flag.
       *
       * <p>
       * If FORMAT_ABBREV_TIME is set and 12-hour time format is used, then the
       * start and end times (if shown) are abbreviated by not showing the minutes
       * if they are zero.  For example, instead of "3:00pm" the time would be
       * abbreviated to "3pm".
       *
       * <p>
       * If FORMAT_ABBREV_WEEKDAY is set, then the weekday (if shown) is
       * abbreviated to a 3-letter string.
       *
       * <p>
       * If FORMAT_ABBREV_MONTH is set, then the month (if shown) is abbreviated
       * to a 3-letter string.
       *
       * <p>
       * If FORMAT_ABBREV_ALL is set, then the weekday and the month (if shown)
       * are abbreviated to 3-letter strings.
       *
       * <p>
       * If FORMAT_NUMERIC_DATE is set, then the date is shown in numeric format
       * instead of using the name of the month.  For example, "12/31/2008"
       * instead of "December 31, 2008".
       *
       * <p>
       * If the end date ends at 12:00am at the beginning of a day, it is
       * formatted as the end of the previous day in two scenarios:
       * <ul>
       *   <li>For single day events. This results in "8pm - midnight" instead of
       *       "Nov 10, 8pm - Nov 11, 12am".</li>
       *   <li>When the time is not displayed. This results in "Nov 10 - 11" for
       *       an event with a start date of Nov 10 and an end date of Nov 12 at
       *       00:00.</li>
       * </ul>
       *
       * @param context the context is required only if the time is shown
       * @param formatter the Formatter used for formatting the date range.
       * Note: be sure to call setLength(0) on StringBuilder passed to
       * the Formatter constructor unless you want the results to accumulate.
       * @param startMillis the start time in UTC milliseconds
       * @param endMillis the end time in UTC milliseconds
       * @param flags a bit mask of options
       * @param timeZone the time zone to compute the string in. Use null for local
       * or if the FORMAT_UTC flag is being used.
       *
       * @return the formatter with the formatted date/time range appended to the string buffer.
       */
      public static Formatter formatDateRange(Context context, Formatter formatter, long startMillis,
                                              long endMillis, int flags, String timeZone) {
          // If we're being asked to format a time without being explicitly told whether to use
          // the 12- or 24-hour clock, icu4c will fall back to the locale's preferred 12/24 format,
          // but we want to fall back to the user's preference.
          if ((flags & (FORMAT_SHOW_TIME | FORMAT_12HOUR | FORMAT_24HOUR)) == FORMAT_SHOW_TIME) {
              flags |= DateFormat.is24HourFormat(context) ? FORMAT_24HOUR : FORMAT_12HOUR;
          }
  
          String range = DateIntervalFormat.formatDateRange(startMillis, endMillis, flags, timeZone);
          try {
              formatter.out().append(range);
          } catch (IOException impossible) {
              throw new AssertionError(impossible);
          }
          return formatter;
      }
  
      /**
       * Formats a date or a time according to the local conventions. There are
       * lots of options that allow the caller to control, for example, if the
       * time is shown, if the day of the week is shown, if the month name is
       * abbreviated, if noon is shown instead of 12pm, and so on. For the
       * complete list of options, see the documentation for
       * {@link #formatDateRange}.
       * <p>
       * Example output strings (date formats in these examples are shown using
       * the US date format convention but that may change depending on the
       * local settings):
       * <ul>
       *   <li>10:15am</li>
       *   <li>3:00pm</li>
       *   <li>3pm</li>
       *   <li>3PM</li>
       *   <li>08:00</li>
       *   <li>17:00</li>
       *   <li>noon</li>
       *   <li>Noon</li>
       *   <li>midnight</li>
       *   <li>Midnight</li>
       *   <li>Oct 31</li>
       *   <li>Oct 31, 2007</li>
       *   <li>October 31, 2007</li>
       *   <li>10am, Oct 31</li>
       *   <li>17:00, Oct 31</li>
       *   <li>Wed</li>
       *   <li>Wednesday</li>
       *   <li>10am, Wed, Oct 31</li>
       *   <li>Wed, Oct 31</li>
       *   <li>Wednesday, Oct 31</li>
       *   <li>Wed, Oct 31, 2007</li>
       *   <li>Wed, October 31</li>
       *   <li>10/31/2007</li>
       * </ul>
       *
       * @param context the context is required only if the time is shown
       * @param millis a point in time in UTC milliseconds
       * @param flags a bit mask of formatting options
       * @return a string containing the formatted date/time.
       */
      public static String formatDateTime(Context context, long millis, int flags) {
          return formatDateRange(context, millis, millis, flags);
      }
  
      /**
       * @return a relative time string to display the time expressed by millis.  Times
       * are counted starting at midnight, which means that assuming that the current
       * time is March 31st, 0:30:
       * <ul>
       *   <li>"millis=0:10 today" will be displayed as "0:10"</li>
       *   <li>"millis=11:30pm the day before" will be displayed as "Mar 30"</li>
       * </ul>
       * If the given millis is in a different year, then the full date is
       * returned in numeric format (e.g., "10/12/2008").
       *
       * @param withPreposition If true, the string returned will include the correct
       * preposition ("at 9:20am", "on 10/12/2008" or "on May 29").
       */
      public static CharSequence getRelativeTimeSpanString(Context c, long millis,
              boolean withPreposition) {
  
          String result;
          long now = System.currentTimeMillis();
          long span = Math.abs(now - millis);
  
          synchronized (DateUtils.class) {
              if (sNowTime == null) {
                  sNowTime = new Time();
              }
  
              if (sThenTime == null) {
                  sThenTime = new Time();
              }
  
              sNowTime.set(now);
              sThenTime.set(millis);
  
              int prepositionId;
              if (span < DAY_IN_MILLIS && sNowTime.weekDay == sThenTime.weekDay) {
                  // Same day
                  int flags = FORMAT_SHOW_TIME;
                  result = formatDateRange(c, millis, millis, flags);
                  prepositionId = R.string.preposition_for_time;
              } else if (sNowTime.year != sThenTime.year) {
                  // Different years
                  int flags = FORMAT_SHOW_DATE | FORMAT_SHOW_YEAR | FORMAT_NUMERIC_DATE;
                  result = formatDateRange(c, millis, millis, flags);
  
                  // This is a date (like "10/31/2008" so use the date preposition)
                  prepositionId = R.string.preposition_for_date;
              } else {
                  // Default
                  int flags = FORMAT_SHOW_DATE | FORMAT_ABBREV_MONTH;
                  result = formatDateRange(c, millis, millis, flags);
                  prepositionId = R.string.preposition_for_date;
              }
              if (withPreposition) {
                  Resources res = c.getResources();
                  result = res.getString(prepositionId, result);
              }
          }
          return result;
      }
  
      /**
       * Convenience function to return relative time string without preposition.
       * @param c context for resources
       * @param millis time in milliseconds
       * @return {@link CharSequence} containing relative time.
       * @see #getRelativeTimeSpanString(Context, long, boolean)
       */
      public static CharSequence getRelativeTimeSpanString(Context c, long millis) {
          return getRelativeTimeSpanString(c, millis, false /* no preposition */);
      }
  
      private static Time sNowTime;
      private static Time sThenTime;
  }
  