1.\" 2.\" $FreeBSD: src/usr.sbin/zic/zdump.8,v 1.7.2.2 2003/03/11 22:31:35 trhodes Exp $ 3.\" 4.Dd December 8, 2013 5.Dt ZDUMP 8 6.Os 7.Sh NAME 8.Nm zdump 9.Nd timezone dumper 10.Sh SYNOPSIS 11.Nm 12.Op Fl vV 13.Op Fl c Bo Ar loyear , Bc Ns Ar hiyear 14.Op Fl t Bo Ar lotime , Bc Ns Ar hitime 15.Op Ar zonename ... 16.Sh DESCRIPTION 17The 18.Nm 19utility prints the current time in each 20.Ar zonename 21named on the command line. 22.Pp 23The following options are available: 24.Bl -tag -width indent 25.It Fl v 26For each 27.Ar zonename 28on the command line, 29print the time at the lowest possible time value, 30the time one day after the lowest possible time value, 31the times both one second before and exactly at 32each detected time discontinuity, 33the time at one day less than the highest possible time value, 34and the time at the highest possible time value, 35Each line ends with 36.Em isdst=1 37if the given time is Daylight Saving Time or 38.Em isdst=0 39otherwise. 40.It Fl V 41Like 42.Fl v , 43except omit the times relative to the extreme time values. 44This generates output that is easier to compare to that of implementations 45with different time representations. 46.It Fl c Bo Ar loyear , Bc Ns Ar hiyear 47Cut off verbose output near the start of the given year(s). 48By default, 49the program cuts off verbose output near the starts of the years -500 and 2500. 50.It Fl t Bo Ar lotime , Bc Ns Ar hitime 51Cut off verbose output at the start of the given time(s), given in decimal 52seconds since 1970-01-01 00:00:00 UTC. 53.El 54.Sh LIMITATIONS 55The 56.Fl v 57option may not be used on systems with floating-point 58.Vt time_t 59values that are neither float nor double. 60.Pp 61Time discontinuities are found by sampling the results returned by 62.Xr localtime 3 63at twelve-hour intervals. 64This works in all real-world cases; 65one can construct artificial time zones for which this fails. 66.Pp 67In the output, 68.Dq UT 69denotes the value returned by 70.Xr gmtime 3 , 71which uses UTC for modern time stamps and some other UT flavor for time 72stamps that predate the introduction of UTC. 73No attempt is currently made to have the output use 74.Dq UTC 75for newer and 76.Dq UT 77for older time stamps, partly because the exact date of the introduction of 78UTC is problematic. 79.Sh SEE ALSO 80.Xr ctime 3 , 81.Xr tzfile 5 , 82.Xr zic 8 83