Re: Time

• To: PEPKE@xxxxxxxxxxxx
• Subject: Re: Time
• From: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
• Date: Thu, 13 Jan 1994 11:04:10 -0700

>Date: Thu, 13 Jan 1994 11:04:32 -0500 (EST)
>From: PEPKE@xxxxxxxxxxxx
>To: netcdfgroup@xxxxxxxxxxxxxxxx
>Subject: Time

In the above message you wrote:

>I have a problem with time.  I have netCDF and the udunits packages.  I want to
>be able to write time-dependent meteorological datasets where the time is
>hours, minutes, and seconds, either local or Zulu time.
>
>I would like to do this, satisfying these conditions:
>
>A) I would like to do it in a standard, de facto standard, or quasistandard
>way.
>
>B) I would like my visualization program to be able to figure out, just by
>looking at the file without my having to press buttons, that the time should be
>displayed as hh:mm:ss.

I would store the times in a netCDF `double' variable with a unit
attribute something like "seconds since 1993-12-15 00:00 UTC".  I'd then
interpret and display the netCDF file in something like the following
manner:

    #include <udunits.h>
    ...

        char    string[128];    /* value & units print-buffer */
        utUnit  unit;           /* input units */
        double  value;          /* input value */
        ...
        if (utIsTime(unit))
        {
            /*
             * We're dealing with a temporal unit.
             */
            int         year, month, day, hour, minute;
            float       second;

            (void) utCalendar(value, unit, &year, &month, &day, &hour, 
                              &minute, &second);
            (void) sprintf(string, "%d-%d-%d %d:%d:%d UTC", year, month,
                           day, hour, minute, (int)second);
        }
        else
        {
            /*
             * We're dealing with a non-temporal unit.
             */
            (void) sprintf(string, "%g ", value);
            (void) utPrint(unit, string + strlen(string));
        }

>Also, is there such a thing as a udunits document?

Yes.  It's the manual page in the UDUNITS package.

--------
Steve Emmerson   <steve@xxxxxxxxxxxxxxxx>

• References:
  • Time
    • From: PEPKE