Setting the time-of-day clock

Once the system has been initialized, it can issue one of two messages, depending on whether or not the time-of-day clock is set.

If the time-of-day (TOD) clock is not set, the system asks you to set it:

* 00 IEA886A TOD CLOCK(S) MUST BE SET

Use the following form of the REPLY command to set the time of day clock:

 
R 00,'[DATE=yyyy.ddd][,CLOCK=hh.mm.ss][,UTC]'

Where yyyy is the year (1924-2042), ddd is the day (001-366), hh is the hour (00-23), mm is the minute (00-59), and ss is the second (00-59). Note that you must specify the year yyyy using four digits.

Note: The apostrophes in the reply are optional.

If you include UTC in your reply, the time and date are Coordinated Universal Time. GMT is obsolete, but will be accepted as an alias of UTC. Without the UTC parameter the system assumes the values are local time and date, and only updates the local time of day offset without affecting UTC.

When you have entered a valid reply to message IEA886A, the system issues message IEA903A, requesting a response. There are two possible responses, depending on the environment in which MVS™ is running. The first requests you to reply U to message IEA903A and, at the exact time that matches the TOD clock setting, press the TOD clock security switch. The second version does not request you to press the TOD clock security switch. You reply U to message IEA903A and, at the exact time that matches the TOD clock setting, press the ENTER key for the reply text. Once you have successfully set the TOD clock, or if the TOD clock is already set but you are allowed to alter it, the system displays the time and date and gives you the option of accepting or changing them:

* id  IEA888A UTC DATE=yyyy.ddd,CLOCK=hh.mm.ss
      IEA888A LOCAL DATE=yyyy.ddd,CLOCK=hh.mm.ss REPLY U, OR UTC/LOCAL TIME

If the values are acceptable, reply ‘U’. If you want to change either the local date or time (or both) or the TOD clock, enter the new value(s) as follows, remembering that you must include the UTC parameter to change the value of the TOD clock:

R id,'[DATE=yyyy.ddd][,CLOCK=hh.mm.ss][,UTC]'

Again, the year yyyy must have four digits, and the apostrophes are optional.

Note: The system automatically issues message IEA888A at IPL time if the OPERATOR PROMPT parameter is included in the active CLOCKxx parmlib member. (See z/OS MVS Initialization and Tuning Guide for details.)

If you specified a different clock setting, the system issues message IEA903A (which was described earlier). If you omitted UTC, the system assumes local date and/or time. Once you have set the new time and/or date, the system re-issues message IEA888A with new values. Reply to the message as described above.

Resetting UTC time causes the system to reset the TOD clock and recalculate the local time value, using the new UTC or GMT and the system time zone constant.

Resetting local time does not affect UTC time or the TOD clock. However, it will cause the system to recalculate the system time zone constant (which is initialized at IPL from the CLOCKxx parmlib member). The new time zone constant remains in effect until either local time is modified again or the next IPL.

All of the real time TQEs get adjusted when the local time is updated. Outstanding real time TQEs have their time adjusted based on the local time change that was made. For the External Timer Reference (ETR) or Server Time Protocol (STP), an external interrupt occurs with the time zone offset change, and the timer supervisor code invokes the same TQE time adjustment routine.

If message IEA888A indicates that both UTC and local time values are incorrect, reset the UTC value first.

Note: Set the TOD clock to a value based on zero being equivalent to 00 hours, 00 minutes, 00 seconds on January 1, 1900 UTC. During an IPL, the TOD clock might contain a value that, relative to this base, is not correct. This can happen, for example, when a customer engineer (C.E.) left the clock in the error state. In such a case, to ensure that the local time and date are correct, specify UTC before setting the local time and date.