Calculate day of the week

H DATFMT(*ISO)
D INDATE          DS
D DATE                            D   DATFMT(*USA) INZ
D   DATE_MM                      2S 0 OVERLAY(DATE:1)
D   DATE_DD                      2S 0 OVERLAY(DATE:4)
D   DATE_YYYY                    4S 0 OVERLAY(DATE:7)
D                 DS
D DEC31                           D   DATFMT(*ISO) INZ(D'0001-12-31')
D   DEC31_YYYY                   4S 0 OVERLAY(DEC31:1)
D Sunday          C                   D'1999-12-19'
D Days            S             15P 0

 * Packed numeric parameters
C     *ENTRY        PLIST
C     DATE_MM       PARM                    G$MM              2 0
C     DATE_DD       PARM                    G$DD              2 0
C     DATE_YYYY     PARM                    G$YYYY            4 0
C                   PARM                    G$DW              1 0

 * Calculate the day of the year (julian days)
 * (Number of days between the input date and the previous Dec 31)
C                   EVAL      DEC31_YYYY = DATE_YYYY - 1
C     DATE          SUBDUR    DEC31         G$JD:*DAYS

 * Calculate the day of the week (0 = Sunday)
C     DATE          SUBDUR    Sunday        Days:*DAYS
C                   DIV       7             DAYS
C                   MVR                     G$DW              1 0
C                   IF        G$DW < 0
C                   EVAL      G$DW = G$DW + 7
C                   ENDIF

C*    G$JD          DSPLY                   G$DW
C                   RETURN

Barbara Morris

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