This is part of Family API which allow to create dual-os version of program runs under OS/2 and DOS

Note: This is legacy API call. It is recommended to use 32-bit equivalent

2021/09/17 04:47 · prokushev · 0 Comments
2021/08/20 03:18 · prokushev · 0 Comments


This call is used to set the date and time that are maintained by the operating system.


DosSetDateTime (DateTime)


  • DateTime (PDATETIME) - input : Address of the date and time structure:
    • hours (UCHAR) - Current hour (0-23)
    • minutes (UCHAR) - Current minute (0-59)
    • seconds (UCHAR) - Current second (0-59)
    • hundredths (UCHAR) - Current hundredth of a second (0-99)
    • day (UCHAR) - Current day (1-31)
    • month (UCHAR) - Current month (1-12)
    • year (USHORT) - Current year (1980-2079)
    • timezone (SHORT) - Minutes west of UTC (Universal Time Coordinate -720 to 720).
    • weekday (UCHAR) - Current day of the week. This value is ignored and is calculated from the other parameter information.

Return Code

rc (USHORT) - return

Return code descriptions are:

  • 0 NO_ERROR


The value of timezone is the difference in minutes between the current time zone and UTC. This is a positive number if earlier than UTC, and negative number if it is later. For Eastern Standard Time this value is 300 (five hours earlier than UTC).

To get the date and time, issue DosGetDateTime. If the application is executing in the OS/2 environment, it is more efficient to obtain these variables by calling DosGetInfoSeg instead of this function. However, applications written to the family API cannot depend on the availability of DosGetInfoSeg.

Not adhering to the limits on any of the parameters results in the return code being set to rc = 327 (ERROR_TS_DATETIME). Also, OS/2 verifies that the day is possible for the month and the year (even for leap year). If the day is not reasonable, OS/2 will also set rc = 327.

Example Code

C Binding

typedef struct _DATETIME {  /* date */
  UCHAR   hours;            /* current hour */
  UCHAR   minutes;          /* current minute */
  UCHAR   seconds;          /* current second */
  UCHAR   hundredths;       /* current hundredths of a second */
  UCHAR   day;              /* current day */
  UCHAR   month;            /* current month */
  USHORT  year;             /* current year */
  SHORT   timezone;         /* minutes of time west of UTC */
  UCHAR   weekday;          /* current day of week */
USHORT    rc = DosSetDateTime(DateTime);
PDATETIME DateTime;      /* Date/time structure */
USHORT    rc;            /* return code */

The following example obtains and prints date and time information. It then changes the system date to 5/10/1987 and prints the updated information.

#include <os2.h>
  DATETIME   DateTime;       /* Structure to hold date/time info. */
  USHORT     rc;
  rc = DosGetDateTime(&DateTime);     /* Address of d/t structure */
  printf("Today is %d-%d-%d; the time is %d:%d\n", DateTime.month,
         DateTime.day, DateTime.year, DateTime.hours, DateTime.minutes);
  DateTime.day = 10;
  DateTime.month = 5;
  DateTime.year = 1987;
  printf("The new date is %d-%d-%d; the time is %d:%d\n", DateTime.month,
         DateTime.day, DateTime.year, DateTime.hours, DateTime.minutes);
  rc = DosSetDateTime(&DateTime);    /* Address of d/t structure */
  printf("rc is %d\n", rc);

MASM Binding

  date_hours      db  ? ;current hour
  date_minutes    db  ? ;current minute
  date_seconds    db  ? ;current second
  date_hundredths db  ? ;current hundredths of a second
  date_day        db  ? ;current day
  date_month      db  ? ;current month
  date_year       dw  ? ;current year
  date_timezone   dw  ? ;minutes of time west of UTC
  date_weekday    db  ? ;current day of week
EXTRN  DosSetDateTime:FAR
PUSH@  OTHER   DateTime      ;Date/time structure
CALL   DosSetDateTime

Returns WORD