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From: ktl@wag240.caltech.edu (Kian-Tat Lim)
Newsgroups: comp.lang.perl
Subject: Re: A head start (was Re: reverse of localtime())
Message-ID: <14036@cit-vax.Caltech.Edu>
Date: 1 Mar 90 01:05:01 GMT
References: <1176@frankland-river.aaii.oz.au> <1990Feb28.160935.28518@iwarp.intel.com>
Sender: news@cit-vax.Caltech.Edu
Reply-To: ktl@wag240.caltech.edu (Kian-Tat Lim)
Organization: California Institute of Technology, Pasadena, CA
Lines: 68
In-reply-to: merlyn@iwarp.intel.com (Randal Schwartz)


	Here's something I put together for a perl-based backup
script.  It only takes a specific date format, but it'll work until
2070 if your Unix uses an unsigned long for times.  Things also get
hairy around standard/daylight changeover time; I haven't looked to
see if it works properly there.

===== CUT HERE =====

sub date2secs {

;# Convert output of "date" to seconds since Jan 1 1970 00:00:00

;# Derived from GNU tar (and others) getdate.y, though not nearly as
;# smart about differing formats

;# Call like this:
;#	do "date2secs.pl";
;#	chop($date = `date`);
;#	$secs = &date2secs($date);

;# Days before first of each month

local(%month) = ("Jan",0,"Feb",31,"Mar",59,"Apr",90,"May",120,"Jun",151,
		 "Jul",181,"Aug",212,"Sep",243,"Oct",273,"Nov",304,"Dec",334);

;# Hours added to each zone to get GMT; single letters are military

local(%zone) = ("nst",3.5,			"ast",4,	"adt",3,
		"est",5,	"edt",4,	"cst",6,	"cdt",5,
		"mst",7,	"mdt",6,	"pst",8,	"pdt",7,
		"yst",9,	"ydt",8,	"hst",10,	"hdt",9,
		"gmt",0,	"bst",-1,	"eet",0,	"eest",-1,
		"met",-1,	"mest",-2,	"wet",-2,	"west",-3,
		"jst",-9,			"aest",-10,	"aesst",-11,
		"acst",-9.5,	"acsst",-10.5,	"awst",-8,
	"a",1,	"b",2,	"c",3,	"d",4,	"e",5,	"f",6,	"g",7,	"h",8,
	"i",9,	"k",10,	"l",11,	"m",12,	"n",-1,	"o",-2,	"p",-3,	"q",-4,
	"r",-5,	"s",-6,	"t",-7,	"u",-8,	"v",-9,	"w",-10,"x",-11,"y",-12,
	"z",0
	);

local($wday,$mm,$dd,$tm,$zz,$yy) = split(/ +/,$_[0]);
$zz =~ tr/A-Z/a-z/;
local($hr,$min,$sec) = split(/[:]/,$tm);

;# Note that the next line will fail in 2070 and the one after will
;# fail in 2101 -- but Unix's signed long for times fails in 2038!
;# We also fail to take into account dates before the epoch (1/1/1970).

$yy += 1900 if $yy < 100; $yy += 100 if $yy <= 69;
local($jdate) = 365 * ($yy - 1970) + int(($yy - 1970 + 1) / 4);
$jdate += $mdays{$mm} + $dd - 1;
$jdate++ if $mm ne "Jan" && $mm ne "Feb" && $yy % 4 == 0 &&
	($yy % 100 != 0 || $yy % 400 == 0);

$jdate *= 86400;
$jdate += (($hr + $zone{$zz}) * 60 + $min) * 60 + $sec;

}

;# Return 1 to indicate successful 'do'
1;

===== CUT HERE =====

--
Kian-Tat Lim (ktl@wagvax.caltech.edu, KTL @ CITCHEM.BITNET, GEnie: K.LIM1)