OSF DCE Administration Guide--Core Components

OSF DCE Administration Guide—Core Components
23.2.5 DTSTime Representation
UTC is the international time standard that has largely replaced GMT. The standard is
administrated by the International Time Bureau (BIH) and is in widespread use. For all
its internal processes, DTS uses opaque binary timestamps that represent UTC. You
cannot read or disassemble a DTS binary timestamp. The DTS API allows other
applications to convert or manipulate the timestamps, but they cannot be displayed. DTS
also translates the binary timestamps into ASCII text for display on a client system.
23.2.5.1 Absolute Time
An absolute time is a point on a time scale. For DTS, absolute times reference the UTC
time scale. Absolute time measurements are derived from system clocks or external
time-providers. When DTS reads a system clock time, the time is recorded in an opaque
binary timestamp that also includes the inaccuracy and other information. When you use
the DCE control program (dcecp) clock show command to display an absolute time, it is
converted to ASCII text, as shown in the following display:
1993-11-21-13:30:25.78523-04:00I010.0825
DTS displays all times in an ISO-compliant format. The International Organization for
Standardization (ISO) format that generated the previous display example is detailed as
shown in Figure 23-4.
Figure 23-4. ISO-Compliant Time Format
CCYY−MM−DD −hh:mm:ss.fff[+|−]hh:mmIsss.fff
Inaccuracy
component
TDF
component
Calendar date and time
component
Century
Year
Month
Day
hour
minute
second
fraction
fractions
seconds
designator
Inaccuracy
minutes
hours
+| − TDF
In the format example shown in the preceding figure, the relative time preceded by the +
(plus sign) or - (minus sign) indicates the hours and minutes that the calendar date and
inaccuracy are offset from UTC. The presence of one of these characters in the string
also indicates that the calendar date and time are the local time of the system, not UTC.
The delineator I indicates the beginning of the inaccuracy component that is associated
with the time. You can express the DTS time that you want to display in several ways.
The DTS time BNF format is defined in Appendix D.
23 − 10 Tandem Computers Incorporated 124243