DragonFly On-Line Manual Pages
ZDUMP(8) DragonFly System Manager's Manual ZDUMP(8)
zdump -- timezone dumper
zdump [-vV] [-c [loyear,]hiyear] [-t [lotime,]hitime] [zonename ...]
The zdump utility prints the current time in each zonename named on the
The following options are available:
-v For each zonename on the command line, print the time at the low-
est possible time value, the time one day after the lowest possi-
ble time value, the times both one second before and exactly at
each detected time discontinuity, the time at one day less than
the highest possible time value, and the time at the highest pos-
sible time value, Each line ends with isdst=1 if the given time
is Daylight Saving Time or isdst=0 otherwise.
-V Like -v, except omit the times relative to the extreme time val-
ues. This generates output that is easier to compare to that of
implementations with different time representations.
Cut off verbose output near the start of the given year(s). By
default, the program cuts off verbose output near the starts of
the years -500 and 2500.
Cut off verbose output at the start of the given time(s), given
in decimal seconds since 1970-01-01 00:00:00 UTC.
The -v option may not be used on systems with floating-point time_t val-
ues that are neither float nor double.
Time discontinuities are found by sampling the results returned by
localtime(3) at twelve-hour intervals. This works in all real-world
cases; one can construct artificial time zones for which this fails.
In the output, ``UT'' denotes the value returned by gmtime(3), which uses
UTC for modern time stamps and some other UT flavor for time stamps that
predate the introduction of UTC. No attempt is currently made to have
the output use ``UTC'' for newer and ``UT'' for older time stamps, partly
because the exact date of the introduction of UTC is problematic.
ctime(3), tzfile(5), zic(8)
DragonFly 4.7 December 8, 2013 DragonFly 4.7