Assembly Language Help (alang.hlp) (Table of Contents; Topic list)
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Int 21h Function 57h
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  Interrupt:   21h     Function:   57h
 
  Title:       Get or Set File Date and Time
 
  See also:    DOS File Date/Time Formats, Get Date, Get Time
 
  Description:
 
     Obtains or modifies the date and time stamp in a file's directory
     entry.
 
     Input                                       Output
 
     If getting date and time                    If function successful
       AH = 57h                                    Carry flag: clear
       AL = 00h                                  And if called with
       BX = Handle                               AL = 00h
                                                   CX = Time
     If setting date and time                      DX = Date
       AH = 57h
       AL = 01h                                  If function unsuccessful
       BX = Handle                                 Carry flag: set
       CX = Time                                   AX = Error code (01h
            Bits 0Bh-0Fh = hours (0-23)                 or 06h)
            Bits 05h-0AH = minutes (0-59)          See: Error codes
            Bits 00h-04h = 2-second increments
                           (0-29)
       DX = Date
            Bits 09h-0Fh = year (relative to
                           1980)
            Bits 05h-08h = month (1-12)
            Bits 00h-04h = day (1-31)
                                    -♦-