Name

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    DATE_CONV

Purpose

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    Procedure to perform conversion of dates to one of three possible formats.

Explanation

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    The following date formats are allowed
      format 1: real*8 scalar encoded as:
              year*1000 + day + hour/24. + min/24./60 + sec/24./60/60
              where day is the day of year (1 to 366)
      format 2: Vector encoded as:
              date[0] = year (eg. 2005)
              date[1] = day of year (1 to 366)
              date[2] = hour
              date[3] = minute
              date[4] = second
      format 3: string (ascii text) encoded as
              DD-MON-YEAR HH:MM:SS.SS
              (eg. 14-JUL-2005 15:25:44.23)
            OR
              YYYY-MM-DD HH:MM:SS.SS (ISO standard)
              (eg. 1987-07-14 15:25:44.23 or 1987-07-14T15:25:44.23)
                 
      format 4: three element vector giving spacecraft time words
      from a Hubble Space Telescope (HST) telemetry packet. Based on
      total number of secs since midnight, JAN. 1, 1979
      format 5: Julian day. As this is also a scalar, like format 1,
      the distinction between the two on input is made based on their
      value. Numbers > 2300000 are interpreted as Julian days.

Calling Sequence

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      results = DATE_CONV( DATE, TYPE )

Inputs

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      DATE - input date in one of the possible formats. Must be scalar.
      TYPE - type of output format desired. If not supplied then
              format 3 (real*8 scalar) is used.
                      valid values:
                      'REAL' - format 1
                      'VECTOR' - format 2
                      'STRING' - format 3
                      'FITS' - YYYY-MM-DDTHH:MM:SS.SS'
                      'JULIAN' - Julian date
                      'MODIFIED' - Modified Julian date (JD-2400000.5)
              TYPE can be abbreviated to the single character strings 'R',
              'V', 'S', 'F', 'J', and 'M'.
              Nobody wants to convert TO spacecraft time (I hope!)

Outputs

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      The converted date is returned as the function value.

Examples

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      IDL> print,date_conv('2006-03-13 19:58:00.00'),f='(f15.5)'
            2006072.83194
      IDL> print,date_conv( 2006072.8319444d,'F')
            2006-03-13T19:58:00.00
      IDL> print,date_conv( 2006072.8319444d,'V')
            2006.00 72.0000 19.0000 57.0000 59.9962
      IDL> print,date_conv( 2006072.8319444d,'J'), f='(f15.5)'
            2453808.33194

History

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      version 1 D. Lindler July, 1987
      adapted for IDL version 2 J. Isensee May, 1990
      Made year 2000 compliant; allow ISO format input jls/acc Oct 1998
      DJL/ACC Jan 1998, Modified to work with dates such as 6-JAN-1996 where
              day of month has only one digit.
      DJL, Nov. 2000, Added input/output format YYYY-MM-DDTHH:MM:SS.SS
      Replace spaces with '0' in output FITS format W.Landsman April 2006
      Added Julian date capabilities on input and output. M.Perrin, July 2007
      Removed spurious /WARN keyword to MESSAGE W.L. Feb 2012