XCalendar

代码说明：

  XCalendar is a collection of calendar utilities for Delphi. As you know the Delphi TDateTime type stores date/times as a floating point value representing the time passed from a specific time, or more precisely: The integral part of a Delphi TDateTime value is the number of days that have passed since 12/30/1899. The fractional part of the TDateTime value is fraction of a 24 hour day that has elapsed. A calendar divides time into units, such as weeks, months, and years. The number, length, and start of the divisions vary in each calendar. So any TDateTime value can be decoded to units of an arbitrary calendar and values expressed in units of a calendar can be encoded to TDateTime values. XCalendar contains calendars, database date/time field types, tools to find calendar events and some astronomical stuff.