SETCLOCK

Use the Date-Time and Correction form of the command for slight adjustmen ts of the system time. F or example, these forms w ould be used to mo ve the time forward or bac kward slightly in order to k eep the system time sync hronized with an external time source. Both local and Univ ersal (GMT) time are adjusted.

Use the Time Zone form of the command for the larger time c hanges required to move the system to a new time zone, suc h as moving between Standard Time and Da ylight Savings Time. This form of the command alters the local time without changing Universal Time.

Date-Time:If the Date-Time form of the command is used, the system time is adjusted to the speci￿ed date and time. This adjustmen t is gradual by default. It may be made immediate if ;NOW is speci￿ed and the user has System Manager (SM) capabilit y.

Correction: If the Correction form of the command is used, the system

time is adjusted forward or bac kward by the amount of the correction. This adjustment is always gradual.

Time Zone: If the Time Zone form is used, local time is adjusted to matc h that of the speci￿ed time zone. In addition, the system time zone o￿set is c hanged to re￿ect the new time zone.

The Use of The Time Zone O￿set

On the HP3000 Univ ersal Time (GMT) is calculated b y starting with local time and adding or subtracting a time zone o￿set. When c hanging time zones (such as moving from Standard to Da ylight Savings Time and bac k) the local time is altered, but this c hange must not a￿ect Universal Time. To prevent Universal Time from being altered, both the local time and the system time zone o￿set must be adjusted. Therefore, using the Time Zone form of this command is the only w ay to accurately change time zones.

If the Date-Time or Correction form of the command is used, Univ ersal Time will drift along with local time. Th us, the Date-Time and Correction forms of this command should only be used to adjust the cloc k for drift, not to c hange time zones.

Results of the Time Zone F orm

2-240 MPE/iX Commands