[gnuastro-commits] master 8361c45: Fits library: can read output when date-time string ends in Z

[Mohammad Akhlaghi]

branch: master
commit 8361c452be919e6b2bf266960c202939f4ad2ed4
Author: Mohammad Akhlaghi <address@hidden>
Commit: Mohammad Akhlaghi <address@hidden>

    Fits library: can read output when date-time string ends in Z
    
    Until now, when the date-time string ended in a `Z' the Fits program's
    `--datetosec' option wouldn't parse it and complain. This is what is
    expected according to the FITS standard. However, unfortunately some FITS
    writers don't follow the standard fully and implement the extended w3.org
    standard (https://www.w3.org/TR/NOTE-datetime).
    
    According to the `w3.org' standard, a `Z' at the end of the string
    signifies that its in UTC (which is the default in FITS). With this commit,
    we just ignore the ending `Z' and use the same steps as before.
    
    This feature was suggested by Zahra Sharbaf.
---
 NEWS       |  5 +++++
 lib/fits.c | 30 ++++++++++++++++++++++--------
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/NEWS b/NEWS
index efd3e2d..95aea82 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,11 @@ See the end of the file for license conditions.
 
   Fits:
    --datasum: Calculate and print the given HDU's "datasum" to stdout.
+   --datetosec: Can also account for `Z' in the end of the date-time
+     string. According to `https://www.w3.org/TR/NOTE-datetime', a `Z'
+     effectively means no time zone, or UTC time (which is the default in
+     FITS). It still doesn't account for time zone hours of the w3.org
+     standard.
 
   MakeCatalog:
    --sigmaclip: defines the sigma-clipping parameters for those columns.
diff --git a/lib/fits.c b/lib/fits.c
index 8ad9c71..72604d4 100644
--- a/lib/fits.c
+++ b/lib/fits.c
@@ -905,12 +905,17 @@ gal_fits_key_clean_str_value(char *string)
 
 /* Fill the `tm' structure (defined in `time.h') with the values derived
    from a FITS format date-string and return the (optional) sub-second
-   information as a double.*/
+   information as a double.
+
+   The basic FITS string is defined under the `DATE' keyword in the FITS
+   standard. For the more complete format which includes timezones, see the
+   W3 standard: https://www.w3.org/TR/NOTE-datetime
+*/
 char *
 gal_fits_key_date_to_struct_tm(char *fitsdate, struct tm *tp)
 {
   char *c=NULL, *cf;
-  int hasT=0, hassq=0, usesdash=0, usesslash=0;
+  int hasT=0, hassq=0, usesdash=0, usesslash=0, hasZ=0;
 
   /* Initialize the `tm' structure to all-zero elements. In particular, The
      FITS standard times are written in UTC, so, the time zone (`tm_zone'
@@ -918,7 +923,7 @@ gal_fits_key_date_to_struct_tm(char *fitsdate, struct tm 
*tp)
      has to be zero. The day-light saving flag (`isdst' element) also has
      to be set to zero. */
   tp->tm_sec=tp->tm_min=tp->tm_hour=tp->tm_mday=tp->tm_mon=tp->tm_year=0;
-  tp->tm_wday=tp->tm_yday=tp->tm_isdst=tp->tm_gmtoff;
+  tp->tm_wday=tp->tm_yday=tp->tm_isdst=tp->tm_gmtoff=0;
   tp->tm_zone=NULL;
 
   /* According to the FITS standard the `T' in the middle of the date and
@@ -931,6 +936,8 @@ gal_fits_key_date_to_struct_tm(char *fitsdate, struct tm 
*tp)
       case '-':  usesdash=1;  break; /* Day definition: YYYY-MM-DD.       */
       case '/':  usesslash=1; break; /* Day definition(old): DD/MM/YY.    */
       case '\'': hassq=1;     break; /* Wholly Wrapped in a single-quote. */
+      case 'Z':  hasZ=1;      break; /* When ends in `Z', means UTC. See  */
+                                   /* https://www.w3.org/TR/NOTE-datetime */
       }
   while(++c<cf);
 
@@ -939,10 +946,14 @@ gal_fits_key_date_to_struct_tm(char *fitsdate, struct tm 
*tp)
         ? NULL
         : ( usesdash
             ? ( hasT
-                ? strptime(fitsdate, hassq?"'%FT%T'":"%FT%T", tp)
+                ? ( hasZ
+                    ? strptime(fitsdate, hassq?"'%FT%TZ'":"%FT%TZ", tp)
+                    : strptime(fitsdate, hassq?"'%FT%T'":"%FT%T", tp) )
                 : strptime(fitsdate, hassq?"'%F'"   :"%F"   , tp))
             : ( hasT
-                ? strptime(fitsdate, hassq?"'%d/%m/%yT%T'":"%d/%m/%yT%T", tp)
+                ? ( hasZ
+                    ? strptime(fitsdate, 
hassq?"'%d/%m/%yT%TZ'":"%d/%m/%yT%TZ", tp)
+                    : strptime(fitsdate, hassq?"'%d/%m/%yT%T'":"%d/%m/%yT%T", 
tp))
                 : strptime(fitsdate, hassq?"'%d/%m/%y'"   :"%d/%m/%y"   , tp)
                 )
             )
@@ -956,9 +967,12 @@ gal_fits_key_date_to_struct_tm(char *fitsdate, struct tm 
*tp)
           "these formats:\n"
           "   YYYY-MM-DD\n"
           "   YYYY-MM-DDThh:mm:ss\n"
-          "   DD/MM/YY               (Note the `YY', see *)\n"
-          "   DD/MM/YYThh:mm:ss      (Note the `YY', see *)\n\n"
-          "[*]: Gnuastro's FITS library (this program), interprets the "
+          "   YYYY-MM-DDThh:mm:ssZ   (Note the `Z',  see *) \n"
+          "   DD/MM/YY               (Note the `YY', see ^)\n"
+          "   DD/MM/YYThh:mm:ss\n"
+          "   DD/MM/YYThh:mm:ssZ\n\n"
+          "[*]: The `Z' is interpreted as being in the UTC Timezone.\n"
+          "[^]: Gnuastro's FITS library (this program), interprets the "
           "older (two character for year) format, year values 68 to 99 as "
           "the years 1969 to 1999 and values 0 to 68 as the years 2000 to "
           "2068.", fitsdate);