[fitsbits] Re: Time and Date fields (24 hour AMPM indicator)

[Peter Teuben]

Kenn Lynch wrote:
> 
> Hello all
> I've found what I believe to be a problem in one of the image
> processing programs I use. Of course it uses it's own compressed
> format quite well. But it creates Fits Date and time fields that
> appear corrupt to me (and apparently some other FIT readers)
> This package is creating data and time fields that contain an AM PM
> indicator that also appears to be swapped with the decimal seconds
> field see the following example
> 
> DATE-OBS= '2000-10-01T2:02:15 PM.1E3'
> 
> The last 3 bytes appear either to be swapped
> with the 3 before the last 3 ?
> 
> or on the other hand maybe it should be in 24 hour
> format begin with '2000-10-01T14:02:15.1??'

yes, the FITS/Y2K standard (which closely follows the ISO
convention) uses a 24 hour clock. No such thing as AM and PM.
You should contact the author of the code that write such
files.

Two good links with information and software are

	http://www.cv.nrao.edu/fits/
and
	http://heasarc.gsfc.nasa.gov/docs/heasarc/fits.html

http://www.cv.nrao.edu/fits/documents/proposals/year2000.txt

Contains the final Y2K agreement how to encode time.

- peter