Pack a Clipper date value down to 50% it's original size.
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 Syntax

        GT_DatePack([<dDate>]) --> cPackedDate

 Arguments:

      <dDate> is the date value to be packed. If not passed it defaults
      to the system date.

 Returns:

      A character string that is a packed version of the date.

 Description:

      GT_DatePack() can be used to pack a date value into half it's
      original size. This can be a help when trying to reduce the size
      requirements of your database files.

 Examples:

      // Place a couple of packed date values into a database.

      Customer->Entry_Date := GT_DatePack()   // Todays date.
      Customer->Call_Date  := GT_DatePack(dCallDate)

 Source: DATEPACK.PRG

 Author:  Dave Pearson