Guardian Procedure Calls Reference Manual

local civil time. There is no way to examine a Julian timestamp and determine which of the
three times it represents.
Procedures that work with the 64-bit Julian timestamp are COMPUTETIMESTAMP,
CONVERTTIMESTAMP, INTERPRETTIMESTAMP, JULIANTIMESTAMP, and
SYSTEMCLOCK_SET_/SETSYSTEMCLOCK.
• Process creation time is initialized by calling TIMESTAMP, which returns the local civil time in
centiseconds (0.01 second = 10 milliseconds) since midnight (00:00) on 31 December 1974,
in an array of three words. Only the two low-order words are saved in the process control
block (PCB); this is sufficient to make the unnamed process ID unique.
• The RCLK instruction ($READCLOCK in TAL) is another source of timestamps. It returns a 64-bit
timestamp representing the local civil time in microseconds since midnight (00:00) on 31
December 1974. Note that this is not a Julian timestamp.
• Process timing uses 64-bit elapsed time counters with microsecond resolution; these are not
Julian timestamps either.
• There is no way to generalize about internal timing using 64-bit Julian timestamps or 48-bit
timestamps. Each section of the operating system manages time using the method most
appropriate for its application.
• All time and calendar units in this discussion are defined in The Astronomical Almanac
published annually by the U.S. Naval Observatory and the Royal Greenwich Observatory.
Example
CALL TIMESTAMP ( TIMESTAMP^BUF );
Related Programming Manual
For programming information about the TIMESTAMP utility procedure, see the Guardian
Programmer's Guide.
TIMESTAMP Procedure 1425