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Xref: sserve comp.unix.bsd:14745 comp.unix.misc:13673 comp.unix.programmer:19605 comp.unix.questions:54293 Newsgroups: comp.unix.bsd,comp.unix.misc,comp.unix.programmer,comp.unix.questions Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!bunyip.cc.uq.oz.au!munnari.oz.au!constellation!convex!hermes.oc.com!news.unt.edu!cs.utexas.edu!swrinde!pipex!sunic!trane.uninett.no!eunet.no!nuug!EU.net!uunet!hobbes!earth.armory.com!spcecdt From: spcecdt@armory.com (John DuBois) Subject: Re: Q: How can I get yesterday's date? Organization: The Armory Date: Sun, 28 Aug 1994 03:39:50 GMT Message-ID: <Cv87IF.1yo@armory.com> References: <Pine.3.89.9408160216.A15886-0100000@worf.uwsp.edu> <32q00b$9vn@daphne.ecmwf.co.uk> <32qdqm$bnv@access1.digex.net> <33ft6h$ecf@trantjern.ifi.uio.no> Sender: news@armory.com (Usenet News) Nntp-Posting-Host: deeptht.armory.com Lines: 25 p10:~> echo $TZ PST8PDT p10:~> date Sat Aug 27 20:06:31 PDT 1994 p10:~> TZ=PST32PDT date Fri Aug 26 20:06:35 PDT 1994 The numeric part of TZ was increased by 24 to go back one day in time. Note, the PST...PDT are needed to get the right timezone into the date. Also, the existance of the part after the numeric offset tells the time functions that the local area does daylight savings time: p10:~> TZ=32 date Fri Aug 26 19:09:30 1994 p10:~> TZ=32x date Fri Aug 26 20:09:40 1994 This scheme wouldn't work with time functions that do an explicit bounds check on the numeric offset (insisting that it be <24), but I've never run into such. You can give a positive or negative offset, including minute & second components, to find the date an arbitrary amount of time (within the bounds of the UNIX time format) in the past/future. John -- John DuBois spcecdt@armory.com KC6QKZ http://www.armory.com/~spcecdt