| Re: How to convert Julian date into Gregorian date format in IDL? [message #89730 is a reply to message #89728] |
Thu, 20 November 2014 14:59  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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mick.mitanirc3@gmail.com writes:
>
> I think the disconnect here is between Julian Date and Julian Day of Year (DOY).
>
> Mr. Hasan's value of 213 is a Julian Day of Year value, in this case 213 days into year 2010. Systime with the /Julian flag returns the Julian Date value - the number of seconds elapsed since 00:00:00 Jan 1 1970 UTC (commonly called the Unix or POSIX Epoch).
>
> The military often use Julian DOY in the form of YYYYDOY or YYDOY and unfortunately usually call the result a Julian Date which wasn't a problem until us programmers came around with our date/time functions.
>
> The JHU library function I mentioned in my first reply works with Julian DOY.
I just want to point out that the built-in Julday function (in
conjunction with CalDat) can also handle the Day of Year number.
IDL> date = 2007118L
IDL> year = Fix(StrMid(StrTrim(date,2), 0, 4))
IDL> dayofyear = Fix(StrMid(StrTrim(date,2), 4, 3))
IDL> CALDAT, JULDAY(1, dayofyear, year), month, day
IDL> Print, month, day
4 28
You can learn more here:
http://www.idlcoyote.com/code_tips/dayofyear.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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