Calendar and Time Formats
RWDateTime allows you to calculate, read, write, and otherwise manipulate dates and times in a wide variety of formats.
NOTE: Classes
RWTimeTuple and
RWTimeTupleOffset also store dates and times but provide no functionality to compare or manipulate dates, offering potentially better performance under certain conditions. In addition, they also offer picosecond precision. See
RWTimeTuple and RWTimeTupleOffset for more information.
UTC (GMT) Dates and Times
Class
RWDateTime represents both time and date, stored as the number of milliseconds since 1 January 1901 UTC (Coordinated Universal Time). UTC is also called GMT, for Greenwich Mean Time, five hours ahead of Eastern Standard Time, although UTC has been the preferred term since it replaced GMT in 1972.
Times given in UTC are almost always given in terms of a 24-hour clock. Thus, 14:42 (often written simply 1442) is 2:42 p.m., and 21:17 (2117) is 9:17 p.m.
UTC is used in Iceland, Liberia, Morocco, Senegal, Ghana, Mali, Mauritania, and several other countries. During the winter months, UTC is also the time scale for the United Kingdom and Ireland.
Proleptic Gregorian Calendar
The Gregorian calendar was introduced by Pope Gregory XIII in 1582, and adopted in various places at various times. It was adopted by England on September 14, 1752, and thus came to the United States.
RWDateTime is based on the proleptic Gregorian calendar, which applies Gregorian calendar rules for all dates, including those prior to its invention in 1582.
