`select parseDateTimeBestEffort('01/12/2017, 18:31:44')`

It is confused by a comma - should be easy to fix.
readDecimalNumber<2>(time_zone_offset_hour, digits);
                        readDecimalNumber<2>(time_zone_offset_minute, digits + 2);
                    }
                    else if (num_digits == 3)
                    {
                        readDecimalNumber<1>(time_zone_offset_hour, digits);
                        readDecimalNumber<2>(time_zone_offset_minute, digits + 1);
                    }
                    else if (num_digits == 2)
                    {
                        readDecimalNumber<2>(time_zone_offset_hour, digits);
                    }
                    else if (num_digits == 1)
                    {
                        readDecimalNumber<1>(time_zone_offset_hour, digits);
                    }
                    else
                        return on_error("Cannot read DateTime: unexpected number of decimal digits for time zone offset: " + toString(num_digits), ErrorCodes::CANNOT_PARSE_DATETIME);
                    if (num_digits < 3 && checkChar(':', in))
                    {
                        num_digits = readDigits(digits, sizeof(digits), in);
                        if (num_digits == 2)
                        {
                            readDecimalNumber<2>(time_zone_offset_minute, digits);
                        }
                        else if (num_digits == 1)
                        {
                            readDecimalNumber<1>(time_zone_offset_minute, digits);
                        }
                        else