Re: timestamps and dates

On Mon, 28 Apr 2003, Tom Lane wrote:

> "Nigel J. Andrews" <nandrews@investsystems.co.uk> writes:
> > In answer to Tom's question in reply about B using leap second accounting, I
> > don't know. Someone here probably can say without thinking whether RH 7.0 did
> > or not.
>
> I believe this is a property of the timezone file you are using.  But
> like you, I dunno what determines the default timezone when neither TZ
> nor /etc/timezone is set.  Anyone?

info libc says this (in the node 'Running make install'):

    To configure the locally used timezone, set the `TZ' environment
    variable.  The script `tzselect' helps you to select the right
    value. As an example, for Germany, `tzselect' would tell you to
    use `TZ='Europe/Berlin''.  For a system wide installation (the
    given paths are for an installation with `--prefix=/usr'), link
    the timezone file which is in `/usr/share/zoneinfo' to the file
    `/etc/localtime'.  For Germany, you might execute `ln -s
    /usr/share/zoneinfo/Europe/Berlin /etc/localtime'.

My system (Gentoo 1.4 w/ glibc 2.3.1) didn't have /etc/timezone at all. So
I did a little googling and found that it's mostly used by programs
tzconfig/tzsetup etc.

And what comes to leap second accounting, the leap seconds were introduced
in 1972 and after that only ~35 leap seconds have been added to UTC.

You could try this on your box (it *might* work):

% date +%s -d '31-dec-1998 23:59:60'
915141600
% date +%s -d '1-jan-1999 00:00:00'
915141600

If there's one second difference in numbers it implies that leap second
accounting is on in your timezone file.

BTW, I found a rather interesting page "Astronomical Time Keeping", which
contains lots of information about timezones, calendars, different UTs,
leap seconds, leap years...: http://www.maa.mhn.de/Scholar/times.html

--
Antti Haapala