In a 24-hour day, a.m. and p.m. refer to the two 12-hour periods of the day. A.m. refers to the period between 12:00 in the morning and 11:59 in the late morning, whereas p.m. refers to the period between 12:00 midday and 11:59 in the late evening.Know More
The abbreviation a.m. is derived from the Latin phrase ante meridiem, which translates to "before midday." The abbreviation p.m., also derived from Latin, stands for post meridiem, which translates to "after midday."
The time designations a.m. and p.m. are used when referring to 12-hour clocks. The 24-hour clock, which is used in the military, eliminates a.m. and p.m., instead using the numbers 0000 through 2400 to refer to hours and minutes, with the first two numbers representing hours and the last two numbers representing minutes.
The terms coordinate with the rising, setting and midday position of the sun. Before precise timekeeping came into use, people could tell the time of day based on the sun's position. For example, when the sun crosses the meridian in a specific geographic location, it is noon, otherwise known as midday, signifying the end of the a.m. period and the beginning of the p.m. period. People residing in the same time zone experience noon at the same time, but as they move through time zones, the time differs in one-hour increments.Learn More
People in the United States set their clocks back at the end of Daylight Savings Time every year, which usually occurs in October or November. Not all countries in the world use Daylight Saving Time, but many do. It is most popular in the Western Hemisphere.Full Answer >
In the Northern Hemisphere, the official summer season begins with the June solstice, which takes place on June 20th, 21st or 22nd each year, and ends with the September equinox, which takes place on September 22nd or 23rd each year; the exact duration of summer depends on when the solstice and equinox will take place and can range from 92 to 95 days. Though summer is associated with warm temperatures and the concept of 'summer break' for students, the season has an official scientific definition, as is defined above. Summer weather in the Northern Hemisphere may begin before the official start of the season and last until after fall has begun with the advent of the September equinox.Full Answer >
There are 52 complete weeks in a year. The year has 365 days, leaving one extra day. A leap year has 366 days, adding a second extra day. This makes 52 1/7 weeks in a normal year and 52 2/7 weeks in a leap year.Full Answer >
The formula for calculating whether a year is a leap year or not is as follows: if a year can be evenly divided by 4 (such as 2012), then it is a leap year unless it can also be evenly divided by 100 (such as 2100). There is one further exception: if a year can be evenly divided by 400 (such as 2000), then it is a leap year.Full Answer >