| Re: Computing Time [message #19382 is a reply to message #19377] |
Mon, 20 March 2000 00:00   |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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loeh@my-deja.com wrote:
>
> Hi,
> I have a couple of measurements and like to calculate the time between
> them. But I am not sure which routine to use.
> I tried the following but the result is confusing
> IDL> diff=JULDAY(3,17,2000,17,30,22)-JULDAY(3,17,2000,15,22,17)
> IDL> print,diff
> 0.088946760
> IDL> CALDAT, diff, Month, Day, Year, Hour, Minute, Second
> IDL> PRINT, Month, Day, Year, Hour, Minute, Second
> 1 1 -4713 14 8
> 5.0000381
> Thanks for help
> Mirko
>
JULDAY will give you fractional days as an answer. To convert this back
into
days, hours, minutes, etc., you can do:
days = fix(diff) ; or long() if you desire
hour = fix( (diff-days)*24. )
minute = fix( (diff-days-hour/24.)*1440. )
second = fix( (diff-days-hour/24.-minute/1440.)*86400. )
just that you may run into roundoff problems here or there. And this is
why you should probably follow Liam's advice and use the JHU APL
routines.
Cheers,
Martin
PS: and to save you from likely headaches: always use DOUBLE if you deal
with time variables (except maybe for storing them in a file)
--
[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[[[[[[
[[ Dr. Martin Schultz Max-Planck-Institut fuer Meteorologie [[
[[ Bundesstr. 55, 20146 Hamburg [[
[[ phone: +49 40 41173-308 [[
[[ fax: +49 40 41173-298 [[
[[ martin.schultz@dkrz.de [[
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