HP C/iX Library Reference Manual (30026-90004)

Appendix A 375
Time Zones
TZTAB Time Zone Adjustment Table
tzname An alphabetic string containing the time zone name or abbreviation. The
tzname value must match either the tzname field in the first line of the
time zone adjustment entry or the
dstzname field in the first line of the
entry.
diff The difference in hours from GMT. Any fractional value of diff is shown
in minutes.
Comments are allowed within time zone adjustment entries. They begin with a pound sign
(#) and include all characters up to a new line. Comments are ignored.
Example
The time zone adjustment entry for the Eastern Time Zone in the United States is as
follows:
EST5EDT
0 3 6 1 1974 0-6 EDT4
0 3 22-28 2 1975 0 EDT4
0 3 24-30 4 1976-1986 0 EDT4
0 3 1-7 4 1987-1999 0 EDT4
0 1 24-30 11 1974 0 EST5
0 1 25-31 10 1975-1999 0 EST5
Normally, Eastern Standard Time (EST) is five hours earlier than Coordinated Universal
Time. This is indicated in the first line. However, during Eastern Daylight Time, the
difference is four hours. The first time Eastern Daylight Time took effect was on January
6, 1974 at 3:00 am EDT. This information is given in the second line. Note that the minute
before was 1:59 am EST. The change back to standard time took effect on the last Sunday
in November of the same year. This information is given on the sixth line. At that point,
the time changed from 1:59 am EDT to 1:00 am EST. The transition to Eastern Daylight
Time since then has gone from the last Sunday in February (indicated on the third line) to
the last Sunday in April (fourth line) to the first Sunday in April (fifth line). The return to
standard time for the same period has consistently occurred on the last Sunday in October
(seventh line).
The TZTAB file was developed by Hewlett-Packard. It can support and is compatible with
Native Language Support (NLS).