The routine sets the date and time that will be used for subsequent history records added to an NDF (both default history records and those added using NDF_HPUT). If no date and time is set using this routine, then the curent date and time will be used. Any date and time established by a previous call to this function can be removed by supplying a blank value for argument "DATE", in which case the current date and time will be used for subsequent history records.

CALL NDF_HSDAT( DATE, INDF, STATUS )

DATE = CHARACTER $\ast$ ( $\ast$ ) (Given)

INDF = INTEGER (Given)

STATUS = INTEGER (Given and Returned)

The formats accepted for the "DATE" argument are listed below. They are all case-insensitive and are generally tolerant of extra white space and alternative field delimiters:

• Gregorian Calendar Date: With the month expressed either as an integer or a 3-character abbreviation, and with optional decimal places to represent a fraction of a day ("1996-10-2" or "1996-Oct-2.6" for example). If no fractional part of a day is given, the time refers to the start of the day (zero hours).

• Gregorian Date and Time: Any calendar date (as above) but with a fraction of a day expressed as hours, minutes and seconds ("1996-Oct-2 12:13:56.985" for example). The date and time can be separated by a space or by a "T" (as used by ISO8601 format).

• Modified Julian Date: With or without decimal places ("MJD 54321.4" for example).

• Julian Date: With or without decimal places ("JD 2454321.9" for example).

• Besselian Epoch: Expressed in decimal years, with or without decimal places ("B1950" or "B1976.13" for example).

• Julian Epoch: Expressed in decimal years, with or without decimal places ("J2000" or "J2100.9" for example).

• Year: Decimal years, with or without decimal places ("1996.8" for example). Such values are interpreted as a Besselian epoch (see above) if less than 1984.0 and as a Julian epoch otherwise.