HP OpenVMS Systems Documentation

Content starts here

DECnet-Plus for OpenVMS
Applications Installation and Advanced Configuration

Previous Contents Index

3.7 Reconfiguring the Time Zone Differential Factor (DECdts)

DECdts binary time values are based on Coordinated Universal Time (UTC), an international time standard that has largely replaced Greenwich Mean Time (GMT) as a reference. For most measurement purposes, UTC is the equivalent of GMT. However, time zones are still determined by their relationship to the prime meridian in Greenwich, England. The local time in each time zone or locale is determined by its offset, or differential, from the Greenwich time zone. This value is commonly expressed as a time differential factor (TDF) of a positive or negative number of hours.

3.7.1 Selecting the DECdts Configuration Option

To reconfigure DECdts, proceed as follows from the Configuration Options menu:

* Which configuration option to perform?            [1] :5

Select Option 5 and press Return.

The system displays:

 DTSS$CONFIG-I-LOGS Deassigning system timezone logicals

 DTSS$CONFIG-I-STOPDTS  Deleting the DTSS Entity

 Node 0 DTSS
 at 1995-08-04-18:36:19.740+00:00Iinf

 Node 0 DTSS
 at 1995-08-04-18:36:23.960+00:00Iinf

        Timezone Options:

        [0]     Exit Timezone Configuration

        [1]     Choose a timezone using menus
        [2]     Use Universal Coordinated Time (UTC)
        [3]     Type in your own timezone rule

* Enter an option number                            [1] :

The following sections explain each of the DECdts menu options.


Changes made to DECdts take effect immediately.

3.7.2 Configuring Your System's Local Time

When you are initially configuring a system, you must determine its geographical location and designate its time zone rule (TZR), which is based on the location. The TZR contains the abbreviated name of the system's time zone and the applicable TDF, so that DECdts can calculate UTC from the system (local) time during the initial configuration of the DECdts software. The TZR also contains information on any seasonal adjustments to the TDF that normally apply in the selected time zone.

If you want to select the commonly accepted TZR for a given area and system, you can use the net$configure procedure menus to select the geographical location of the system. Based on your selection, the net$configure procedure automatically sets the TZR. After you configure your system, it displays the local time even though the DECdts software uses UTC in the background. Because the default value of the DECdts management attribute Automatic TDF Change is TRUE, DECdts also changes the displayed local time automatically if there is a seasonal adjustment to the system's TDF.

In rare instances, you may want to customize the TZR for your system, thereby modifying its TDF from the one that normally applies in a given time zone or location. The net$configure menus also provide a selection for entering a custom TZR for your system, although you must know the TZR syntax to enter it. See Section for further information on customizing the system's TZR.

After the initial system configuration, you can reconfigure the system's time zone rule (TZR) by selecting Option 5 in the top-level net$configure menu. For example, this may be necessary because you moved the system to a different location. To reconfigure the TZR, you must know the system's geographical location, or in some cases, the time zone. If you do not know the system's time zone and the configuration procedure requires you to enter it for your locale, refer to the world time zone map in the DECnet-Plus DECdts Management guide. Additionally, when you reconfigure the DECdts software, you are given the option of setting the system's time to UTC time or customizing the system's time to any time zone. Configuring Your System's Local Time Using Menus (Menu Option 1)

Option 1 of the Timezone Options menu allows you to choose the geographical region and conventional TZR for the system. DECdts uses the TZR to automatically convert UTC to the local time whenever the time is displayed. To use Option 1, proceed as follows:

* Enter an option number                           [1] :

Press Return to select Option 1.

The procedure displays a menu of continental regions:

         Timezone Region Options:

        [0]     Return to the Timezone Options menu

        [1]     Europe
        [2]     North America
        [3]     Central & South America
        [4]     Africa
        [5]     Asia
        [6]     South Pacific
        [7]     Antarctica

* Enter a timezone region number                        :2

Enter the option number for the region where the system resides and press Return, or return to the previous menu by typing 0.

If you select a region, the procedure displays a menu of subregions within the region you select. The subregion you select determines the time zone rule for the system. For example, if you enter Option 2 (North America), the procedure displays the following menu:

         Timezone Subregion Options:

       [0]     Return to Region Options menu

       [1]     US/Eastern
       [2]     US/East-Indiana
       [3]     US/Central
       [4]     US/Mountain
       [5]     US/Pacific
       [6]     US/Alaska
       [7]     US/Arizona
       [8]     US/Navajo
       [9]     US/Michigan
       [10]    US/Aleutian
       [11]    US/Hawaii
       [12]    US/Samoa
       [13]    Canada/Newfoundland
       [14]    Canada/Atlantic
       [15]    Canada/Eastern
       [16]    Canada/Central
       [17]    Canada/East-Saskatchewan
       [18]    Canada/Mountain
       [19]    Canada/Pacific
       [20]    Canada/Yukon

* Enter a timezone subregion number                   : 1

Enter the option corresponding to the subregion where the system resides; in the example, the system is in the eastern United States. After you make a selection, the procedure executes and displays information on the NCL DTSS module subroutines that initialize the DECdts software with the new settings:

DTSS$CONFIG-I-LOGS Defining system timezone logicals
DTSS$CONFIG-I-SETLCL Setting Local Clock
%RUN-S-PROC_ID, identification of created process is 00000059

Node 0 DTSS
at 1995-02-25-08:17:29.520-05:00Iinf

Node 0 DTSS
at 1995-02-25-08:17:30.790-05:00Iinf

Node 0 Event Dispatcher Outbound Stream *
at 1995-02-25-08:17:30.950-04:00Iinf

Node 0 DTSS
at 1995-02-25-08:17:39.978-05:00I0.327

Node 0 DTSS
at 1995-02-25-08:17:45.868-05:00I0.328


   Automatic TDF Change = True

Node 0 DTSS
at 1995-02-25-08:17:51.898-05:00I0.328

%RUN-S-PROC_ID, identification of created process is 0000006B

Node 0 DTSS
at 1995-02-25-08:18:06.138-05:00Iinf

Node 0 DTSS
at 1995-02-25-08:18:07.488-05:00Iinf

Node 0 Event Dispatcher Outbound Stream *
at 1995-02-25-08:18:08.560-04:00Iinf

This completes changes to DECdts configuration using Option 1. Configuring Your System's Local Time as UTC (Menu Option 2)

If your system is located in the GMT time zone or Antarctica, and you do not want to make seasonal adjustments to the TDF, you may want to use UTC as your system's local time. You can also configure all network systems with UTC if you consider local time irrelevant for your applications. If you select UTC as the local time and later enter the NCL command show dtss current time, the local time displayed has a TDF of 0 (zero).

The following example shows how to select UTC for the system's local time.

         Timezone Options:

        [0]     Exit Timezone Configuration

        [1]     Choose a timezone using menus
        [2]     Use Universal Coordinated Time (UTC)
        [3]     Type in your own timezone rule

* Enter an option number                            [1] :2 Customizing Your System's Time Zone Rule (Menu Option 3)

The net$configure procedure allows you to create a customized time zone rule (TZR) for your system, rather than selecting a location and having the procedure configure a TZR for you. When you create a customized TZR, you must supply the correct abbreviation for the system's time zone, the zone's offset from GMT, and optional seasonal time-change information. If you do not know the system's time zone or time zone abbreviation, see Table 3-2 in this book, and the world time zone map in the appendix of the DECnet-Plus DECdts Management guide.

The following example shows the TZR syntax and describes the TZR fields; you can also display similar information by typing a question mark (?) after you choose Option 3 from the Timezone Options menu.

         Timezone Options:

        [0]     Exit Timezone Configuration

        [1]     Choose a timezone using menus
        [2]     Use Universal Coordinated Time (UTC)
        [3]     Type in your own timezone rule

* Enter an option number                                 [1] :3

Specify three or more characters that are the designation for the standard ( STD) or summer/daylight-saving time ( DST) time zone. The variable STD is required; if DST is missing, then summer time does not apply in this locale. Uppercase and lowercase letters are explicitly allowed. Any characters except a numeral, comma (,), minus ( - ), plus (+), space, and ASCII NUL are allowed.
offset Specifies the value to be added to the local time to arrive at UTC. The offset has the format hh[: mm[: ss]]; the hour ( hh) is required and can be a single digit. The minutes ( mm) and seconds ( ss) are optional. One or more digits can be used; the value is always interpreted as a decimal number. The hour must be between zero and 24; the minutes and seconds (if present) between zero and 59. If preceded by a minus ( - ), the time zone is east of Greenwich; if preceded by a (+) or not signed, it is west of Greenwich. Note that the signing conventions are based on POSIX rules, which reverse ISO signing conventions.
Indicate when to change to and from summer time. The variable start describes the date of the change to summer time, and end describes the date of the change back to standard time. The start and end format follows:
  • J n --- The Julian day n (1 < n < 365). Leap days are not counted. That is, in all years (including leap years) February 28 is day 59 and March 1 is day 60. It is impossible to explicitly refer to the occasional February 29.
  • n --- The zero-based Julian day (0 < n < 365). Leap days are counted, and it is possible to refer to February 29.
  • M m. n. d --- The nth d day of month m (1 < n < 5, 0 < d < 6, 1 < m < 12). When n is 5 it refers to the last d day of month m. Day 0 is Sunday.
  • time --- The time field describes the time when, in current time, the change to or from summer time occurs. The variable time has the same format as offset except that no leading sign ( - or +) is allowed. The default, if time is not given, is 02:00:00.

As an example of a typical TZR, if the rule has the value EST5EDT4,M4.1.0,M10.5.0, it describes the rule for the eastern United States, which became effective in 1987. EST is the designation for Eastern Standard Time, which is 5 hours behind GMT. EDT is the designation for Eastern Daylight-Saving Time, which is 4 hours behind GMT. EDT starts on the first Sunday in April and ends on the last Sunday in October. In both cases, because the time is not specified, the change to and from EDT occurs at the default time of 2:00 a.m.

Since the TZR format is complex, you may want to refer to Table 3-2 to copy the rule for your locale onto the command line, and then edit the rule as desired.

Table 3-2 Time Zone Rules
Region Name Time Zone Rule Notes
Eastern European Time EET-2EET_DST-3,M3.5.0/3,M9.5.0/3  
Iceland WET0  
Middle European Time MET-1MET_DST-2,M3.5.0/2,M9.5.0/2  
Poland MET-1MET_DST-2,M3.5.0/1,M9.5.0/1  
Turkey EET-3EET_DST-4,M3.5.0/1,M9.5.0/1  
UK-Ireland GMT0BST-1,M3.5.0/1,M10.5.0/1  
Western European Time WET0WET_DST-1,M3.5.0/1,M9.5.0/1  
North America    
Canada/Atlantic AST4ADT3,M4.1.0/2,M10.5.0/2  
Canada/Central CST6CDT5,M4.1.0/2,M10.5.0/2  
Canada/Eastern EST5EDT4,M4.1.0/2,M10.5.0/2  
Canada/East-Saskatchewan CST6  
Canada/Mountain MST7MDT6,M4.1.0/2,M10.5.0/2  
Canada/Newfoundland NST3:30NDT2:30,M4.1.0/2,M10.5.0/2  
Canada/Pacific PST8PDT7,M4.1.0/2,M10.5.0/2  
Canada/Yukon YST9YDT8,M4.1.0/2,M10.5.0/2  
US/Alaska AKST9AKDT8,M4.1.0/2,M10.5.0/2  
US/Aleutian HAST10HAST9,M4.1.0/2,M10.5.0/2  
US/Arizona MST7  
US/Central CST6CDT5,M4.1.0/2,M10.5.0/2  
US/Eastern EST5EDT4,M4.1.0/2,M10.5.0/2  
US/East-Indiana EST5  
US/Hawaii HST10  
US/Michigan EST5EDT4,M4.1.0/2,M10.5.0/2  
US/Mountain MST7MDT6,M4.1.0/2,M10.5.0/2  
US/Navajo MST7MDT6,M4.1.0/2,M10.5.0/2  
US/Pacific PST8PDT7,M4.1.0/2,M10.5.0/2  
US/Samoa SST11  
Central & South America    
Brazil/Acre AST5ADT4,M10.4.6/2,M2.2.6/2  
Brazil/DeNoronha FST2FDT1,M10.4.6/2,M2.2.6/2  
Brazil/East EST3EDT2,M10.4.6/2,M2.2.6/2  
Brazil/West WST4WDT3,M10.4.6/2,M2.2.6/2  
Chile/Easter EST6EDT5,M10.2.0/0,M3.2.0/0 (Easter Islands)
Chile/Regional CST4CDT3,M10.2.0/0,M3.2.0/0  
Cuba CST5CDT4,M5.2.0/0,M10.2.0/0  
Jamaica EST5EDT4,M4.1.0/2,M10.5.0/2  
Mexico/General CST6  
Mexico/BajaNorte PST8PDT7,M4.1.0/2,M10.5.0/2  
Mexico/BajaSur MST7  
Egypt EET-2EET_DST-3,J152/2,J305/2  
Libya EET-2EET_DST-3,J121/2,J303/2  
Hong Kong HKT-8  
Iran IST-3:30IDT-4:30,M3.5.0/2,M9.3.0/2  
Israel IST-3IDT-4,M4.3.0/2,M8.4.6/2  
Japan JST-9  
PRC CST-8CDT-9,M4.2.0/2,M9.2.0/3  
ROK KST-9KDT-10,M5.2.0/2,M10.2.0/3  
Singapore SST-8  
South Pacific    
Australia/North CST-9:30  
Australia/NSW EST-10EST-11,M10.5.0/2,M3.1.0/3  
Australia/Queensland EST-10 (Standard Time)
Australia/Queensland EST-10EST-11,M10.5.0/2,M3.1.0/3 (NSW time)
Australia/South CST-9:30CST-10:30,M10.4.0/2,M3.3.0/3  
Australia/Tasmania EST-10EST-11,M10.4.0/2,M3.3.0/3  
Australia/Victoria EST-10EST-11,M10.4.0/2,M3.3.0/3  
Australia/West WST-8  
New Zealand NZST-12NZDT-13,M10.5.0/2,M3.1.0/3  
Antarctica UTC0  

Previous Next Contents Index