NAME

   dts_intro - Introduction to DCE Distributed Time Service (DTS)

 DESCRIPTION

   The DCE Distributed Time Service programming routines can obtain time-
   stamps that are based on Coordinated Universal Time (UTC), translate
   between different timestamp formats, and perform calculations on time-
   stamps. Applications can call the DTS routines from server or clerk
   systems and use the timestamps that DTS supplies to determine event
   sequencing, duration, and scheduling.

   The DTS routines can perform the following basic functions:

     +  Retrieve the current (UTC-based) time from DTS.

     +  Convert binary timestamps expressed in the utc time structure
        to or from tm structure components.

     +  Convert the binary timestamps expressed in the utc time structure
        to or from timespec structure components.

     +  Convert the binary timestamps expressed in the utc time structure
        to or from ASCII strings.

     +  Compare two binary time values.

     +  Calculate binary time values.

     +  Obtain time zone information.

   DTS can convert between several types of binary time structures that
   are based on different calendars and time unit measurements. DTS uses
   UTC-based time structures, and can convert other types of time
   structures to its own presentation of UTC-based time.

   Absolute time is an interval on a time scale; absolute time measurements
   are derived from system clocks or external time-providers.  For DTS,
   absolute times reference the UTC standard and include the inaccuracy and
   other information.  When you display an absolute time, DTS converts the
   time to ASCII text, as shown in the following display:

        1992-11-21-13:30:25.785-04:00I000.082

   Relative time is a discrete time interval that is often added to or sub-
   tracted from an absolute time. A TDF associated with an absolute time is
   one example of a relative time.  Note that a  relative time does not use
   the calendar date fields, since these fields concern absolute time.

   Coordinated Universal Time (UTC) is the international time standard that
   DTS uses.  The zero hour of UTC is based on the zero hour of Greenwich
   Mean Time (GMT).  The documentation consistently refers to the time zone
   of the Greenwich Meridian as GMT.  However, this time zone is also some-
   times referred to as UTC.

   The Time Differential Factor (TDF) is the difference between UTC and the
   time in a particular time zone.

   The user's environment determines the time zone rule (details are system
   dependent).

   If the user's environment does not specify a time zone rule, the
   system's rule is used (details of the rule are system dependent).
   For example, on OpenVMS systems, the rule pointed to by the filename
   in SYS$SYSTEM:SYS$TIMEZONE_SRC.DAT applies.

   The OSF DCE Application Development Guide provides additional infor-
   mation about UTC and GMT, TDF and time zones, and relative and absolute
   times.

   Unless otherwise specified, the default input and output parameters are
   as follows:

     +  If NULL is specified for a utc input parameter, the current time is
        used.

     +  If NULL is specified for any output parameter, no result is
        returned.

 RELATED INFORMATION

   Books: OSF DCE Application Development Guide