converting from one timezone to another

[keak]

Hi there,
Is there an efficent way to convert from one timezone to another or to add or subtract hours in either perl or bash system call?

I have something like (eastern time)
2005-7-30T18:00:00

and I need to say subtract 3 hours and change it to (GMT time)
2005-08-14T13:30:00Z

any input on this will be appriciated.

 

[MikeLacey]

Hi keak,

If you only need to convert between GM time and Local time you can use the gmtime() and localtime() functions; they both take the output of the time() function which gives the number of seconds that have elapsed since some date or other which I can never remember.

If you want to add an hour to a particular time you can do it like this:

$my_time = time();
$my_time = $my_time + (60 * 60);
$my_time = $my_time + (2* (60 * 60)); # or add two hours
$my_time = $my_time - (3* (60 * 60)); # or subtract 3 hours


Mike

I am not inscrutable.

Want great answers to your Tek-Tips questions? Have a look at faq219-2884

 

[KevinADC]

hopefully you are working with the raw time stamp returned from time(). Mike gave some examples, here is another:

my $time = gmtime(time-3600);

where 3600 is 60 * 60, the number of seconds in an hour.

 

[rharsh]

I'm nitpicking here, but EST is GMT - 5 hours. So to get from EST to GMT, you'd need to add 5 hours, not subtract 3.

 

[KevinADC]

I was being very general in my answer, I assumed the OP could extrapolate from the examples Mike and I provided, but I could also be wrong and your "nitpicking" will help them out if thats the case mate. Team work!

 

[rharsh]

Kevin (and Mike too) - your answers are great, my comment was more for the OP. After seeing this:

have something like (eastern time)
2005-7-30T18:00:00

and I need to say subtract 3 hours and change it to (GMT time)
2005-08-14T13:30:00Z

I was concerned that the OP might be subtracting 3 hours and expecting GMT.

 

[PaulTEG]

Maybe the OP is just looking for the GMT equivalent of 3 hours before the time given ;-)