Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!gatech!udel!princeton!jonlab!jon
From: jon@jonlab.UUCP (Jon H. LaBadie)
Newsgroups: comp.unix.questions
Subject: Re: Date: Can it be specific to a shell??
Summary: one minor adjustment is possible
Message-ID: <806@jonlab.UUCP>
Date: 12 Sep 89 13:09:06 GMT
References: <72074@yale-celray.yale.UUCP> <1138@virtech.UUCP>
Distribution: usa
Organization: 4455 Province Line Rd., Princeton, NJ 08540
Lines: 33

In article <1138@virtech.UUCP>, cpcahil@virtech.UUCP (Conor P. Cahill) writes:
> In article <72074@yale-celray.yale.UUCP>, zador-anthony@CS.YALE.EDU (anthony zador) writes:
> >  How does the UNIX date command know the date?
> It performs a time(2) system call which gets the current time in seconds
> (actually this is the count of seconds since Jan 1, 1970 12:00am GMT), the
> ctime(3) library call is then used to generate the date that we all know
> and love.
> 
> > Must date be the same to all shells on a given machine, 
> 
> Yup.
> 
> > or can su selectively adjust the date for a given shell?
> 
> Nope.

One minor adjustment is possible.

As ctime(3) must adjust the GMT system clock for the local timezone,
a particlular instance of a shell could set the TZ environment variable
to something other than the actual timezone.

Some systems may also allow fractional offsets.

Try:
	$ TZ=KST-12KDT ; date		# Time in Korea

	$ TZ=Twi300000Lit ; date	# Time in the Twilite Zone

-- 
Jon LaBadie
{att, princeton, bcr}!jonlab!jon
{att, attmail, bcr}!auxnj!jon