Document revision date: 19 July 1999

One of the steps in setting the correct time on your system is to calculate a time differential factor (TDF) for your time zone.

The TDF associates each local time zone with UTC; it is the difference between your local system time and UTC. The TDF changes each time your local system time undergoes a time zone change; the UTC, on the other hand, does not change.

The TDF value is expressed in signed (+ or -) hh:mm format. The Americas have negative TDFs, while Europe, Africa, Asia, and Australia have positive TDFs.

Section 5.9.2 explains how to select the correct TDF for your time zone.

5.9.1.3 Daylight Saving Time and Standard Time

Typically, you make seasonal changes to the local system time (for example, for daylight saving time and standard time). You usually adjust the local time one hour forward or backward.

You also need to adjust the TDF to compensate for the new local system time. You adjust the TDF in the same direction as the local time; that is, when you add an hour to the local time, you also add an hour to the TDF.

5.9.1.4 Time Zones

Time zones are names for geographical areas that share the same TDF; they also share the same rule or rules for seasonal changes between standard time and daylight saving time.

5.9.2 Determining Your System's Time Differential Factor

You can use the map in Figure 5-1 to determine the TDF for your time zone. If you prefer, you can use the tables in Appendix B in the OpenVMS System Manager's Manual to determine the standard or daylight saving time TDF for your time zone. The procedure described in Section 5.9.3 shows default TDF values for various time zones.

To use the map to determine the TDF of your time zone, follow these steps:

1. Find your location on the map and notice the time zone band at that location.
2. Follow the time zone band to the top of the map, and note the TDF that corresponds to your time zone. For example, the TDF for California is --8:00; the TDF for Italy is +1:00.

Some time zones do not have full-hour TDFs. In these cases, find the specific value on the map itself. For example, if you live in Adelaide, Australia, your TDF is +9:30.

If your time zone has daylight saving time, your TDF for daylight saving time is typically +1:00 from the standard time. For example, if your standard time TDF is +2:00, your daylight saving time TDF is +3:00; if your standard time TDF is -7:00, your daylight saving time TDF is -6:00.

Figure 5-1 Time Differential Factor Map

5.9.3 Using UTC$TIME_SETUP.COM

• To set your local time zone or your TDF, or both.
• To modify your system's local time to adjust for daylight saving or standard time.
• To display the local time and TDF for your system.

If you set the time zone and the TDF on one node in a cluster, the values you set take effect on other nodes in the cluster when those nodes are rebooted.

For your convenience, the instructions for using the command procedure have been split into two sections:

• Setting the time zone
• Setting the TDF

Beginning the Procedure

To use SYS$MANAGER:UTC$TIME_SETUP.COM, follow these steps:

1. Log in to the SYSTEM account, or enter the following command to enable LOG_IO and OPER privileges:

   $ SET PROCESS/PRIVILEGES=(LOG_IO,OPER)

2. Enter the following command to start UTC$TIME_SETUP.COM:

   $ @SYS$MANAGER:UTC$TIME_SETUP.COM

   %UTC-I-UPDTIME, updating Time Zone information in SYS$COMMON:[SYSEXE]

3. Press Return to accept the default of BOTH, or enter one of the other choices in answer to the following question:

   Configure which time parameter (TIMEZONE/TDF/BOTH/NONE)? [BOTH]

   Note Compaq recommends that you set both the time zone and the TDF. If you set the TDF without setting the time zone, the procedure cannot provide default TDF values.

If you answer BOTH or TIMEZONE to the time parameter question in the command procedure, continue with the next section. If you answer TDF to the question, skip to Section 5.9.3.2.

5.9.3.1 Setting the Time Zone on Your System

The local time zone is the location you want to consider your default local time zone. Usually this local time zone is the same as the local time zone in which your system is located.

You set the local time zone by making choices in a command procedure.

The system first displays the following information:

Configuring the Local Time Zone TIME ZONE SPECIFICATION -- Main Time Zone Menu 1) Australia 11) GMT 21) Mexico 31) Turkey 2) Brazil 12) Greenwich 22) NZ 32) UCT 3) CET 13) Hong Kong 23) NZ-CHAT 33) US 4) Canada 14) Iceland 24) Navajo 34) UTC 5) Chile 15) Iran 25) PRC 35) Universal 6) Cuba 16) Israel 26) Poland 36) W-SU 7) EET 17) Jamaica 27) ROC 37) WET 8) Egypt 18) Japan 28) ROK 38) Zulu 9) Factory 19) Libya 29) Singapore 10) GB-Eire 20) MET 30) SystemV 0) None of the above

Table 5-5 lists and describes the acronyms that appear in the Main Time Zone Menu.

Table 5-5 Time Zone Acronyms

Time Zone Acronym	Description
CET	Central European Time
EET	Eastern European Time
Factory	Specifies no time zone
GB-Eire	Great Britain/Ireland
GMT	Greenwich Mean Time
MET	Middle European Time
NZ	New Zealand
NZ-CHAT	New Zealand, Chatham Islands
PRC	People's Republic of China
ROC	Republic of China
ROK	Republic of Korea
SystemV	Specific to System V operating system
UCT	Coordinated Universal Time
US	United States
UTC	Coordinated Universal Time
Universal	Coordinated Universal Time
W-SU	Middle European Time
WET	Western European Time

To select a time zone, follow these steps:

1. Enter a number after the following question; for example, 33, for the United States:

   Select the number above that best describes your location: 33

   
   If you enter 0, the system defaults to GMT.

2. If you enter a country that has more than one time zone, the system displays a message and asks for a confirmation like the following one (if not, skip to the explanation following step 4):

   You selected US as your time zone. Is this correct? (Yes/No) [YES]: [Return]

3. The system displays areas with different time zones and asks you to select your area. Enter a number, for example, 6:

   US Time Zone Menu 1) Alaska 4) Central 7) Hawaii 10) Mountain 2) Aleutian 5) East-Indiana 8) Indiana-Starke 11) Pacific 3) Arizona 6) Eastern 9) Michigan 12) Samoa 0) None of the above

   Select the number above that best describes your location: 6

4. Confirm the displayed information, or enter another number after the following prompt; for example:

   You selected US/Eastern as your time zone. Is this correct? (Yes/No) [YES]: [Return]

   
   When you confirm the last statement, the system redefines the following system logical names:

   • sys$localtime
   • sys$posixrules
   
   The DEC C RTL uses these logical names to compute the time zone rules for your applications. The system also writes this information to sys$timezone.dat. The system uses this file to reset sys$localtime and sys$posixrules when you reboot.
   The system then displays the TDFs for standard and daylight saving time that correspond to the time zone you have selected:

   Default Time Differential Factor for standard time is -5:00. *Default Time Differential Factor for daylight saving time is -4:00.

   
   * The system displays daylight saving time only for time zones that use daylight saving time.

If you answer TDF or BOTH to the time parameter question at the beginning of the command procedure, the system displays prompts for the TDF on your system.

To set the TDF, answer the following questions:

1. Select option 2 to display the TDF the system has calculated for you:

   Configuring the Time Differential Factor (TDF) Enter ? anytime for help [0] Exit [1] Set the Time Differential Factor [2] Display the Time Differential Factor

   Please pick an option number [2]: 2

   
   The system displays information like the following items:

   SYSTEM TIME DIFFERENTIAL FACTOR = -4:00 (-14400 seconds). LOCAL SYSTEM TIME = 22-SEP-1998 10:49:45.20.

2. Select option 1 to verify the TDF displayed or to enter a new one:

   Configuring the Time Differential Factor (TDF) Enter ? anytime for help [0] Exit [1] Set the Time Differential Factor [2] Display the Time Differential Factor

   Please pick an option number [2]: 1

   
   The system then displays the following information:

   The Time Differential Factor (TDF) is the difference between your system time and Coordinated Universal Time (UTC). UTC is similar in most repects to Greenwich Mean Time (GMT). The TDF is expressed as hours and minutes, and should be entered in the hh:mm format. TDFs for the Americas will be negative (-3:00, -4:00, etc.); TDFs for Europe, Africa, Asia and Australia will be positive (1:00, 2:00, etc.).

   
   The system displays the following question only if you set the time zone as well. However, some time zones do not have daylight saving time; if they do not, the system also does not display this question.

3. Answer Yes or No to the following question:

   Is Daylight Saving time in effect? (Yes/No):

4. After the following prompt, either press Return to accept the displayed default or enter the correct TDF. (If you have not set the time zone, the system does not display a default TDF value.)

   Enter the Time Differential Factor [-4:00]:

   
   The system then explains the need to modify the system time as well for season time changes:

   If this is a seasonal time change, it may also be necessary to modify the system time. Generally, seasonal time changes result in adding 1:00 hour, or adding -1:00 hour to the system time.

5. To the following question, answer Yes if you need to modify the local system time or No if you do not:

   Do you wish to modify the local system time [N]:

   
   If you answer Yes, the system will lead you through a dialogue similar to the one in Section 5.9.4.
   If you answer No, the system next displays the new TDF:

   NEW SYSTEM TIME DIFFERENTIAL FACTOR = -4:00.

6. Answer Yes to confirm the displayed TDF or No if it is incorrect:

   Is this correct? [Y]:

   
   If you answer No, the system returns to step 1 in this section.
   If you answer Yes, the system displays both the TDF and the local system time.

   SYSTEM TIME DIFFERENTIAL FACTOR = -4:00 (-14400 seconds). LOCAL SYSTEM TIME = 22-SEP-1998 10:52:37.36.

To adjust the local time to daylight saving or standard time, you can invoke the command procedure SYS$EXAMPLES:DAYLIGHT_SAVINGS.COM to perform both of the following tasks:

• Adjust the TDF
• Modify the local time

DAYLIGHT_SAVINGS.COM allows you to perform either of the following actions:

• Make the changes immediately. (Usually, however, you would use UTC$TIME_SETUP.COM to make changes immediately by answering Yes to Question 5 in Section 5.9.3.2.)
• Queue a batch job to make the changes at a future time. (This is the most common use of this command procedure.)

The following example of DAYLIGHT_SAVINGS.COM shows answers that cause the procedure to queue a batch job, DST_CHANGE, which will execute when the time changes from standard time to daylight saving time. Many of the questions are similar to those explained in Section 5.9.3.2.

In the example, the initial TDF value is -5:00. The local date and time are any time from the date in 1997 when the change to standard time was made, until 23-APR-1998:02:00, when the change to daylight saving time will be made.

$ SYS$EXAMPLES:DAYLIGHT_SAVINGS This procedure queues a batch job that changes the system time and system time differential around a daylight saving time change. Press the question mark (?) key at any time for help; hit Control-C to exit. The Time Differential Factor (TDF) is the difference between your system time and Coordinated Universal Time (UTC). The difference is expressed in hh:mm format. The Americas have negative offsets from UTC, while Europe, Africa, Asia and Australia have positive offsets from UTC. * Enter the Time Differential Factor: -4:00 [Return] If this is a seasonal time change, it may also be necessary to modify the system time. Generally, seasonal time changes result in adding 1:00 hour, or adding -1:00 hour to the local time. * Do you wish to modify the local system time [N]: Y [Return] Enter the time value you would like to add to the local time. The value can be a positive or a negative (-hh:mm) value. * Enter the time value: +1:00 [Return] The process to modify your time zone offset and local time (if supplied) can occur now or in the future. Press Return to run the job now. * Enter the run time in the DD-MMM-YYYY:HH:MM:SS format: 23-apr-1998:02:00 [Return] NEW SYSTEM TIME DIFFERENTIAL FACTOR = -4:00. ADDING 1:00 TO THE LOCAL TIME. JOB RUN TIME : 23-APR-1998:02:00 * Continue? [Y]: Y [Return] Job DST_CHANGE (queue SYS$BATCH, entry 2) holding until 23-APR-1998 02:00 Batch Job DST_CHANGE scheduled to run at 23-APR-1998:02:00 $ $!!The batch job DST_CHANGE will run on 23-Apr-1998 at 02:00

5.9.5 Setting Time in an OpenVMS Cluster Environment

The TDF and the local time must be the same on all nodes in an OpenVMS Cluster environment. You can use the System Management utility (SYSMAN) DO command to invoke the command procedure UTC$CONFIGURE_TDF.COM on one node in a cluster to perform the following actions for one or more nodes in the cluster:

• Display the TDF
• Set or change the TDF
• Modify the local time

Note that UTC$CONFIGURE_TDF.COM is normally run by UTC$TIME_SETUP.COM when you select the TDF or BOTH option.

You specify the function SET or SHOW, the TDF value, and the local time modification as command procedure parameters. Note that you must express the TDF and the change to the local time in minutes format, not in hours and minutes hh:mm format, as you do if you use the command procedure interactively. For example, for +2:00, you would enter +120 or 120.

Examples

1. The following example changes the TDF clusterwide by +1:00 to 11:00 and also moves the local time ahead by 1 hour, as you would do if you were changing from standard time to daylight saving time. The initial TDF value is +10:00, and the local date and time are 12-MAR-1998:15:20.

   $ RUN SYS$SYSTEM:SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER

   %SYSMAN-I-ENV, Current command environment: Clusterwide on local cluster Username SMITH will be used on nonlocal nodes

   SYSMAN> DO @SYS$MANAGER:UTC$CONFIGURE_TDF SET +660 +60

2. The following example displays the TDF for each node in the cluster:

   $ RUN SYS$SYSTEM:SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER

   %SYSMAN-I-ENV, Current command environment: Clusterwide on local cluster Username SMITH will be used on nonlocal nodes

   SYSMAN> DO @SYS$MANAGER:UTC$CONFIGURE_TDF SHOW

   
   The system will display the TDF and the local time on each node in the cluster.

3. The following command procedure can be submitted as a batch job to run at a future time to perform the following actions:
   • Change the TDF clusterwide by --1:00, to --4:30. (The initial TDF value is --3:30.)
   • Move the local time back by 1 hour.

   $! TO_STANDARD_TIME.COM $! Command procedure to change the TDF by -1:00 and also modify local time $ RUN SYS$SYSTEM:SYSMAN SET ENVIRONMENT/CLUSTER DO @SYS$MANAGER:UTC$CONFIGURE_TDF SET -270 -60 EXIT

   
   Note: Because UTC$CONFIGURE_TDF.COM accepts time in minutes, -4:30 is expressed as -((4 x 60) + 30) or -270; -1:00 is expressed as -60.
   The following command submits this command procedure as a batch job to run at 23-JAN1998:02:00:

   $ SUBMIT/AFTER=23-JAN1998:02:00 TO_STANDARD_TIME.COM

The OpenVMS Alpha architecture maintains the current date and time in the Battery-Backed Watch (BBW) across power failures and system downtime. The BBW is functionally equivalent to the Time of Day Register (TODR) that the VAX architecture uses. One difference, however, is the BBW's constraint on the date range.

The BBW provides sufficient storage capability for only a century. The OpenVMS Alpha system date range has been redefined as 1957 to 2056 to maintain correct leap-year processing and to provide for the millennial transition.

In addition, the OpenVMS Alpha timing mechanisms have been changed to allow 2-digit year support in the $ASCTIM system service and the DCL command SET TIME. (Prior to this change, only 4-digit year fields were allowed.) With 2-digit support, you need to enter only the last 2 digits of a year. The century associated with the year field is derived from the placement of the 2 digits in the 1957-2056 date range. For example:

$ SET TIME = 1-NOV-98

In this example, 98 is the equivalent of 1998.

$ SET TIME = 1-NOV-05

In this example, 05 is the equivalent of 2005.

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