/****************************************************************************
*                                                                           *
*   DT2EXCEL.SPL Copyright 2021 (C) DSP Development Corporation             *
*                                                                           *
*   Author:      Randy Race                                                 *
*                                                                           *
*   Synopsis:    Converts Julian date and seconds to EXCEL timestamps       *
*                                                                           *
*   Revisions:   18 Jan 2021     RRR     Creation                           *
*                                                                           *
****************************************************************************/


#if @HELP_DT2EXCEL

    DT2EXCEL

    Purpose: Converts Julian date and clock seconds to EXCEL timestamps.

    Syntax:  DT2EXCEL(date, time)

              date - Optional. A string or integer julian date, the input date.
                     Defaults to the current date.

              time - Optional. A string or real TOD, the input time. Defaults
                     to the current time.

    Returns: A scalar or series of Excel timestamps

    Example:
             edt = dt2excel("1-1-2021", "12:00:00");
             dte = excel2dt(edt);

             edt = 44197.5
             dte = "1/1/2021 12:00:00.000"

    Example:
             W1: {julstr("1-1-1999"), julstr("1-10-1999"), julstr("4-2-1999")}
             W2: {todstr("12:00"), todstr("14:00"), todstr("9:35")}
             W3: dt2excel(w1, w2)
             W4: excel2dt(w3)

             W3 == {36161.5, 36170.583333, 36252.399306}

             W4 contains the date and time values:

              01/01/1999  12:00:00.000
              01/10/1999  14:00:00:000
              04/02/1999   9:35:00.000

    Remarks:
             An EXCEL timestamp is a real value that represents the
             number of days that have elapsed since 12-30-1899. The
             integer part is the whole number of days and the
             fractional part is the fraction of a day.

             See EXCEL2DT to convert an Excel timestamp to a
             Julian date and clock time value.

    See Also:
             DT2UNIX
             DTXY
             EXCEL2DT
             JULSTR
             LOCAL2UTC
             STRJUL
             STRTOD
             TODSTR
             UNIX2DT
             UTC2LOCAL
             XYDT
#endif


/* convert date and time to excel timestamp */
dt2excel(date = getdate(), time = gettime(13), startdate = "1899/12/30")
{
        local xldt;

        (date, time, startdate) = dt2_parse_args(date, time, startdate);

        /* excel timestamps for each pair of date/time columns */
        xldt = dt2excel_iterate(date, time, startdate);

        return(xldt);
}


ITERATE dt2excel_iterate(date, time, startdate)
{
        local xldt;

        /* excel date offset */
        xldt = date - julstr(startdate) + time / 86400;

        return(xldt);
}