Here's the dst.pl script - cut and paste:
Rgds...Geoff
-------------------------------
#!/usr/bin/perl -w
# Display DST transition times
use English;
use strict;
use Time::Local;
use POSIX qw(strftime);
use Getopt::Std;
use constant VRSN => '[1.04]';
# 1.0 09/14/1998 acs
# 1.01 01/03/2001 acs changed '%e' strftime format specifier to '%d' because
# stupid Windows does not understand real strftime
# 1.02 09/10/2003 acs minor change; subtract 1900 from $year command-line arg;
# the code works w/o this change but this is more proper
# 1.03 09/12/2003 acs added -n option to print only the next time change
# 1.04 10/01/2003 acs added -d option to output days (integer) until next time
# change
use constant SECONDS_PER_DAY => (24 * 60 * 60);
use constant FALSE => 0;
use constant TRUE => 1;
use constant TWO_DATES_MODE => 0;
use constant NEXT_MODE => 1;
use constant DAYS_LEFT_MODE => 2;
# ---------------------------------------------------------------
sub problem
{
my $msg = $_[0];
my $err = $_[1];
printf STDERR ("%s: %s (%d).\n",$PROGRAM_NAME,$msg,$err);
printf STDERR ("\n");
return($err);
} # problem
sub usage
{
printf STDERR
("\nUsage: %s [-y year | -n | -d] [-e] [-u]\n\n",
$PROGRAM_NAME);
printf STDERR
(" -y year - determine time changes for year; by default, the current\n");
printf STDERR
(" year is used.\n");
printf STDERR
(" -n - display only the next time change.\n");
printf STDERR
(" -d - display remaining days until next time change.\n");
printf STDERR
(" -u - print this usage message on stderr and exit.\n");
printf STDERR
(" -e - print the epoch seconds rather than the formatted times\n");
printf STDERR
(" if used with -d, display integer rather than fractional\n");
printf STDERR
(" days remaining until next time change.\n\n");
printf STDERR
("If successful, %s returns a zero result and writes two lines on\n",
$PROGRAM_NAME);
printf STDERR
("stdout of this form:\n");
printf STDERR
(" Sun Apr 5 01:59:59 CST 1998 --> Sun Apr 5 03:00:00 CDT 1998\n");
printf STDERR
(" Sun Oct 25 01:59:59 CDT 1998 --> Sun Oct 25 01:00:00 CST 1998\n");
printf STDERR
(" OR (if using -e option)\n");
printf STDERR
(" 891763199 --> 891763200\n");
printf STDERR
(" 909298799 --> 909298800\n\n");
printf STDERR
("These indicate the time displayed at the transition time and that\n");
printf STDERR
("displayed 1 second later.\n\n");
printf STDERR
("A non-zero result is returned if no TZ is known or no time transition\n");
printf STDERR
("occurs.\n\n");
printf STDERR
("Vrsn %s\n",VRSN);
return(1);
} # usage
sub find_dst # returns the last epoch second $target_isdst is in effect
{
use integer;
my $lo = $_[0];
my $max_hi = $_[1];
my $initial_interval = $_[2];
my $target_isdst = $_[3];
my ($begin_seconds,$next_seconds) = (-1,-1);
my $isdst = FALSE;
# advance by one interval until DST changes
my $hi = $lo;
my $fnd = FALSE;
my $hi_knt = 0;
while (!($fnd) && ($hi <= $max_hi) && ($hi_knt < 2))
{
$isdst = (localtime($hi))[8];
if ($isdst != $target_isdst)
{
$fnd = TRUE;
}
else
{
$lo = $hi;
$hi += $initial_interval;
if ($hi > $max_hi)
{
$hi = $max_hi;
++$hi_knt;
}
}
}
if ($fnd) # now start looking within $interval
{
my $go_down = TRUE;
my $tmp_seconds = $hi;
my $interval = ($hi - $lo) / 2;
while ($interval > 0)
{
if ($go_down)
{
$tmp_seconds = $hi - $interval;
$isdst = (localtime($tmp_seconds))[8];
if ($isdst == $target_isdst)
{
$go_down = FALSE;
$lo = $tmp_seconds;
}
else
{
$hi = $tmp_seconds;
}
}
else
{
$tmp_seconds = $lo + $interval;
$isdst = (localtime($tmp_seconds))[8];
if ($isdst != $target_isdst)
{
$go_down = TRUE;
$hi = $tmp_seconds;
}
else
{
$lo = $tmp_seconds;
}
}
$interval = ($hi - $lo) / 2;
}
if (((localtime($tmp_seconds))[8]) !=
((localtime($tmp_seconds + 1))[8]))
{
$begin_seconds = $tmp_seconds;
$next_seconds = $tmp_seconds + 1;
}
else
{
$begin_seconds = $tmp_seconds - 1;
$next_seconds = $tmp_seconds;
}
}
return($begin_seconds,$next_seconds);
} # find_dst
my $year = -1;
my $cc = 0;
my $do_format = TRUE;
my $yr_arg_knt = 0;
my $mode = TWO_DATES_MODE;
my $now = 0;
our ($opt_y,$opt_n,$opt_d,$opt_u,$opt_e);
if (!getopts('y:ndue'))
{
$cc = 252;
usage();
exit($cc);
}
if (defined($opt_y))
{
$year = $opt_y - 1900;
++$yr_arg_knt;
}
if (defined($opt_n))
{
$mode = NEXT_MODE;
++$yr_arg_knt;
}
if (defined($opt_d))
{
$mode = DAYS_LEFT_MODE;
++$yr_arg_knt;
}
if (defined($opt_e))
{
$do_format = FALSE;
}
if (defined($opt_u))
{
$cc = 251;
usage();
exit($cc);
}
if ($yr_arg_knt > 1 && $cc == 0)
{
$cc = 255;
problem("Only one -n or -y argument allowed",$cc);
}
if ($year <= 0)
{
$now = time();
$year = (localtime($now))[5];
}
if ($cc != 0)
{
exit($cc);
}
$cc = 2;
if (($mode == NEXT_MODE) || ($mode == DAYS_LEFT_MODE))
{
my $isdst_now = (localtime($now))[8];
my $seconds_Dec31 = timelocal(59,59,23,31,11,$year + 1);
my ($start1,$start2) = find_dst($now,$seconds_Dec31,
SECONDS_PER_DAY,$isdst_now);
if ($start1 > 0)
{
if ($mode == NEXT_MODE)
{
if ($do_format)
{
print strftime("%a %b %d %H:%M:%S %Z %Y",localtime($start1)),
" --> ",
strftime("%a %b %d %H:%M:%S %Z %Y",localtime($start2)),
"\n";
}
else
{
print $start1," --> ",$start2,"\n";
}
}
else
{
if ($do_format)
{
printf("%.4f\n",(($start2 - $now) / SECONDS_PER_DAY));
}
else
{
printf("%d\n",int(($start2 - $now) / SECONDS_PER_DAY));
}
}
$cc = 0;
}
}
else
{
my $seconds_Jan1 = timelocal(0,0,0,1,0,$year);
my $isdst_Jan1 = (localtime($seconds_Jan1))[8];
my $seconds_Dec31 = timelocal(59,59,23,31,11,$year);
my ($start1,$start2) = find_dst($seconds_Jan1,$seconds_Dec31,
SECONDS_PER_DAY,$isdst_Jan1);
if ($start1 > 0)
{
$cc = 1;
if ($do_format)
{
print strftime("%a %b %d %H:%M:%S %Z %Y",localtime($start1)),
" --> ",
strftime("%a %b %d %H:%M:%S %Z %Y",localtime($start2)),
"\n";
}
else
{
print $start1," --> ",$start2,"\n";
}
my ($end1,$end2) = find_dst($start2,$seconds_Dec31,
SECONDS_PER_DAY,!($isdst_Jan1));
if ($end1 > 0)
{
if ($do_format)
{
print strftime("%a %b %d %H:%M:%S %Z %Y",localtime($end1)),
" --> ",
strftime("%a %b %d %H:%M:%S %Z %Y",localtime($end2)),
"\n";
}
else
{
print $end1," --> ",$end2,"\n";
}
$cc = 0;
}
}
}
exit($cc);
Proverbs 3:5,6 Trust in the Lord with all your heart and lean not on your own understanding; in all your ways acknowledge him, and he will make all your paths straight.
