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libIGCM_date
This ksh library handles date calculs and convertions in different calendars. 
#==================================================================
function IGCM_date_DaysInYear
* Purpose: Return the number of days in a year
* Usage: IGCM_date_DaysInYear yyyy
         if there is no argument on the command line, 
         then assume that a yyyy is being piped in

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function IGCM_date_DaysInMonth
* Purpose: Calculate the number of days in a month 
* Usage: IGCM_date_DaysInMonth yyyy mm
         or IGCM_date_DaysInMonth yyyymmdd
         if there are no command line arguments then 
         assume that a yyyymmdd is being piped in and read the value.
         if there is only one argument assume it is a yyyymmdd on the command line
         other wise it is a yyyy and mm on the command line
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function IGCM_date_ConvertGregorianDateToJulian
* Purpose: Convert yyyymmdd to yyyyddd
* Usage: IGCM_date_ConvertGregorianDateToJulian 19980429
         if there is no command line argument, then assume that the date"
         is coming in on a pipe and use read to collect it

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function IGCM_date_ConvertJulianDateToGregorian()
* Purpose: Convert yyyyddd to yyyymmdd
* Usage: IGCM_date_ConvertJulianDateToGregorian 1998213
         if there is no command line argument, assume one is being 
         piped in and read it

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function IGCM_date_AddDaysToJulianDate
* Purpose: Add days to a yyyyddd formatted date
* Usage: IGCM_date_AddDaysToJulianDate 1998312 { ,-}14
         Read from the difference from the command lines
         and the date from the command line, or standard input

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function IGCM_date_AddDaysToGregorianDate
* Purpose: Add days to a yyyymmdd formatted date
* Usage: IGCM_date_AddDaysToGregorianDate 19980312 { ,-}14
         Read from the difference from the command lines
         and the date from the command line, or standard input

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function IGCM_date_DaysBetweenJulianDate
* Purpose: Calculate the days difference between two dates and reports 
           the number days as jul1 - jul2 
* Usage: IGCM_date_DaysBetweenJulianDate jul1 jul2
         where julian date is in the form yyyyddd

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function IGCM_date_DaysBetweenGregorianDate ()
* Purpose: Calculate the days difference between two dates and reports 
           the number days as grg1 - grg2 
* Usage: IGCM_date_DaysBetweenGregorianDate grg1 grg2
         where gregorian date is in the form yyyymmdd

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function IGCM_date_DaysSinceJC ()
* Purpose: Calculate the days difference between a date and 00010101
* Usage: IGCM_date_DaysSinceJC grg1
         where gregorian date is in the form yyyymmdd

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function IGCM_date_Check
 * Purpose: Check the present file by comparison with a reference file