Introduction Date/Time Functions


     This section contains functions that make many date computations easier
     to perform.  Date-type values have been a feature of the xBASE language
     standard, and is preserved in Clipper.  In spite of this, it is
     always necessary to develop UDFs to execute certain technical financial
     computations.  Clipper Tools offers an alternative that not only
     spares you the work of writing a UDF, but also provides implementation
     in Assembler to guarantee fast execution.

     This chapter also contains clock time functions.  These include time
     changes, time span computations, time control of loops, and memory-
     resident clock display.

     Please note that valid date tests are already carried out in Clipper.
     Clipper internal date tests cannot be canceled, so it is impossible
     to implement an individual UDF for error handling , if there is an
     invalid date.

     Clipper always replaces an invalid date with a null date.  These
     internal tests are carried out by keyboard input, as well as by CTOD()
     allocation.  For this reason, there are no examples with invalid dates
     in the date function descriptions.  Rather, the result of a function
     with a null date is shown.

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