Technical data

6
Setting System Time
This chapter describes how to control system time on OpenVMS systems,
describes how system time relates to Universal Coordinated Time (UTC), and
tells how to ensure that local system time remains correct when local time
changes, as for daylight saving time. This chapter describes the following tasks:
Task System Section
Setting time zone information OpenVMS Alpha Version 7.3 Section 6.2
Setting time zone information OpenVMS Alpha before
Version 7.3 and OpenVMS
VAX
Section 6.3
Setting time zone information OpenVMS Cluster Section 6.4
Controlling daylight saving time
conversions
All Section 6.5
Setting time using the Battery-
Backed Watch (BBW)
OpenVMS Alpha Section 6.6
Choosing languages, and date
and time formats
OpenVMS Section 6.7
Saving your time customizations OpenVMS VAX and Alpha Section 6.8
Using SYSMAN to manage
system time
Section 6.9
6.1 Setting Correct Time Zone Information on Your System
Beginning with OpenVMS Version 7.0, Comapq C RTL implements its default
date/time support for programs compiled with Compaq C Version 5.2 and later
using a model based on Coordinated Universal Time (UTC), an international
standard for measuring time of day.
Note
Even if you do not use the Compaq C RTL directly, you must set correct
time zone information on your system because other system utilities
written in the Compaq C language might require it.
6.1.1 Distributed Time Synchronization Service (DTSS)
Your system may be using Distributed Time Synchronization Service (DTSS).
DTSS is provided as an option with DECnet-Plus and the Distributed Computing
Environment (DCE). If you are using DTSS, you must not use the procedures
described in this chapter. Instead, use the procedures supplied with DTSS to set
time zone information.
Setting System Time 6–1