[bug #61976] Table arithmetic date-to-sec produces inaccurate result

[Pedram Ashofteh Ardakani]

URL:
  <https://savannah.gnu.org/bugs/?61976>

                 Summary: Table arithmetic date-to-sec produces inaccurate
result
                 Project: GNU Astronomy Utilities
            Submitted by: pedram
            Submitted on: Tue 01 Feb 2022 06:18:37 PM UTC
                Category: Table
                Severity: 3 - Normal
              Item Group: Output not reasonable
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

This bug was first reported by Zohreh Ghaffari.

== steps to reproduce ==

1. create a dummy fits file
2. add the DATE-OBS keyword with value 2018-05-04T04:16:46.7774
3. run table arithmetic to get the 'date-to-sec' result
4. update the DATE-OBS keyword with value 2018-05-04T04:15:25.8326
5. you'd get the same number of seconds for both even though they are about 80
seconds different


$ echo "1" > dummy.txt
$ astconvertt dummy.txt -odummy.fits
$ astfits dummy.fits -h1 --update=DATE-OBS,2018-05-04T04:16:46.7774
$ astfits dummy.fits -h1 --keyvalue=DATE-OBS --colinfoinstdout | \
  asttable -c'arith DATE-OBS date-to-sec' --colinfoinstdout
# Column 1: UNIXSEC [sec,f64,] Unix seconds (from 00:00:00 UTC, 1 January
1970)
1525410945

$ astfits dummy.fits -h1 --update=DATE-OBS,2018-05-04T04:15:25.8326
$ astfits dummy.fits -h1 --keyvalue=DATE-OBS --colinfoinstdout | \
  asttable -c'arith DATE-OBS date-to-sec' --colinfoinstdout
# Column 1: UNIXSEC [sec,f64,] Unix seconds (from 00:00:00 UTC, 1 January
1970)
1525410945





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