OSF DCE Application Development Guide--Core Components

OSF DCE Application Development Guide—Core Components
19.1 DTS Time Representation
UTC is the international time standard that has largely replaced Greenwich Mean Time
(GMT). The standard is administered by the International Time Bureau (BIH) and is
widely used. DTS uses opaque binary timestamps that represent UTC for all of its
internal processes. You cannot read or disassemble a DTS binary timestamp; the DTS
API allows applications to convert or manipulate timestamps, but they cannot be
displayed. DTS also translates the binary timestamps into ASCII text strings, which can
be displayed.
19.1.1 Absolute Time Representation
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, it records the time in an opaque
binary timestamp that also includes the inaccuracy and other information. When you
display an absolute time, DTS converts the time to ASCII text as shown in the following
display:
1990-11-21-13:30:25.785-04:00I000.082
DTS displays all times in a format that complies with the International Organization for
Standardization (ISO) 8601 (1988) standard. Note that the inaccuracy portion of the time
is not defined in the ISO standard; times that do not include an inaccuracy are accepted.
Figure 19-1 explains the ISO format that generated the previous display.
Figure 19-1. ISO Format for Time Displays
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 this figure, the relative time preceded by the + (plus) or - (minus) character indicates
the hours and minutes that the calendar date and time are offset from UTC. The presence
of this time differential factor (TDF) in the string also indicates that the calendar date and
time are the local time of the system, not UTC. Local time is UTC plus the TDF. The
Inaccuracy (I) designator indicates the beginning of the inaccuracy component
19 − 2 Tandem Computers Incorporated 124245