GammaLib

I propose to extend the IRAF parameter interface by adding a new parameter type t that handles times. The reasoning is that a time can be specified in various formats, for example an UTC string, a MJD floating point value, or a mission elapsed (native) time. The handling of the different formats can be done at the interface level, and corresponding time() methods will allow to set and get the times using the GTime class.

The format of the input string need some discussion. UTC strings (e.g. 2016-10-05T15:08:56) should be supported, and providing a simple floating point value (e.g. 1800.0) should (probably) set the native format in TT for compliance with previous applications. Here a possible list of strings that may be supported (list incomplete):

• "2016-10-05T15:08:56" (UTC string)
• "1800.0" (MET seconds in native reference, TT system)
• "1800.0 (UTC)" (MET seconds in native reference, UTC time system)
• "1800.0 (TAI)" (MET seconds in native reference, TAI time system)
• "MJD 54609" (Modified Julian Days, TT system)
• "MJD 54609 (TT)" (Modified Julian Days, TT system)
• "MJD 54609 (UTC)" (Modified Julian Days, UTC system)
• "JD 54609 (TAI)" (Julian Days, TAI system)

Spaces in the strings should be optional (i.e. "JD54609(TAI)" should be valid).

Here an example of a possible parfile:

tmin, t, a, 2016-10-05T08:00:00,,, "Start time" 
tmax, t, a, 2016-10-05T10:00:00,,, "Stop time" 

The following methods should be added to GApplicationPar:

void  time(const GTime& value);
GTime time(void);
void  check_value_time(const std::string& value) const;