7.9.4 Using JP1/AJS3 in a time zone with daylight saving time

When you use JP1/AJS3 in a time zone where daylight saving time applies, the following start times are affected:

Start times of jobnets registered for execution by JP1/AJS3 - View
Start times of jobnets registered for execution by the ajsentry command
Start times of submits jobs registered by the jpqjobsub command with the -st option specified
Start times of processing to delete job information

The following describes the effects of switching from standard time to daylight saving time, and vice versa. Take these effects into consideration when you define the start times for each process. The following figure uses Eastern U.S. standard time in 1994 (TZ=EST5EDT) as an example of a time zone with daylight saving time.

Figure 7‒22: Example of switching between standard time and daylight saving time

Supplementary note

Although the displayed time changes as a result of the switch between standard time and daylight saving time, the flow of time is continuous.

When one second elapses from 1:59:59 on April 7 in standard time, the displayed time becomes 3:00:00 on April 7 in daylight saving time. When one second elapses from 1:59:59 on October 27 in daylight saving time, the displayed time becomes 1:00:00 on October 27 in standard time.

Organization of this subsection

(1) Switching from standard time to daylight saving time
(2) Switching from daylight saving time to standard time
(3) About the displayed start and end times of a unit execution period during which daylight saving time starts or ends

(1) Switching from standard time to daylight saving time

The timing with which processes start after the system switches from standard time to daylight saving time is determined from the start time set for the process, and the time at which the transition from standard time to daylight saving time takes place. The following explanation is based on the example shown in Figure 7-22. When the time reaches 2:00:00 on April 7th, the clock switches to daylight saving time. At this point, the new time will be 3:00:00 on April 7th (this is transition (1) 4/7 1:59:59 → 4/7 3:00:00 in Figure 7-22). This means that the period from 2:00:00 to 2:59:59 is skipped over. If you set up a process to start within this period, it will start at 3:00:00 daylight saving time. If you set it up to start at 3:00:00 or later standard time, the process will start at 3:00:00 or later after the transition to daylight saving time has taken place. This means that the process will start, in relative terms, one hour ahead of its scheduled start time. The following table shows how processes are scheduled around the transition from standard time to daylight saving time.

Table 7‒8: Scheduling at the transition from standard time to daylight saving time
Start time setting	1:59:59 or earlier	2:00:00 to 2:59:59	3:00:00 or later
Actual start time	Executed at 1:59:59 or earlier standard time	Executed at 3:00:00 daylight saving time	Executed at 3:00:00 or later daylight saving time

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(2) Switching from daylight saving time to standard time

The timing with which processes start after the system switches from daylight saving time to standard time is determined from the start time set for the process, and the time at which the transition from daylight saving time to standard time takes place. The following explanation is based on the example shown in Figure 7-22. When the time reaches 2:00:00 (DST) on October 27th, the clock switches to standard time. At this point the new time will be 1:00:00 standard time on October 27th (this is transition (2) 10/27 1:59:59 → 10/27 1:00:00 in Figure 7-22). The result is an extra hour in standard time, from 1:00:00 to 2:00:00. However, processes that were scheduled to start between 1:00:00 and 1:59:59 are started at the scheduled time in daylight saving time, and are not started again after the transition from daylight saving time to standard time. If you set up a process to start at 2:00:00 daylight saving time or later, it will start at 2:00:00 in standard time, after the transition from daylight saving time to standard time has taken place. This means that the process will start, in relative terms, one hour later than its scheduled start time. The following table shows how processes are scheduled around the transition from daylight saving time to standard time.

Table 7‒9: Scheduling at the transition from daylight saving time to standard time
Start time setting	0:59:59 or earlier	1:00:00 to 1:59:59	2:00:00 or later
Actual start time	Executed at 0:59:59 daylight saving time or earlier	Executed between 1:00:00 and 1:59:59 daylight saving time	Executed at 2:00:00 standard time or later

Cautionary notes

If JP1/AJS3 - View and JP1/AJS3 - Manager run on different hosts, make sure that both hosts use the same time zone. For details, see 2.2.2(2) Operation with multiple manager hosts in the JP1/Automatic Job Management System 3 System Design (Configuration) Guide and Cautionary notes in 4.2.1 Types of JP1/AJS3 services in the JP1/Automatic Job Management System 3 System Design (Configuration) Guide.
When you use the ajsentry command to register a jobnet for execution, the schedule of the jobnet depends on the time zone setting used when you execute the ajsentry command. For details, see 2.2.2(2) Operation with multiple manager hosts in the JP1/Automatic Job Management System 3 System Design (Configuration) Guide.
When you register a submit job for execution using the jpqjobsub command with the -st option specified, the job's start time depends on the time zone setting of the manager host that registers the job.

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(3) About the displayed start and end times of a unit execution period during which daylight saving time starts or ends

(a) Display of the (scheduled) execution start and end times

If JP1/AJS3 is operating in a time zone that uses daylight saving time, the (scheduled) execution start and end times are individually displayed based on the time zone that is used at that time. Therefore, if daylight saving time starts or ends between the (scheduled) unit execution start and end times, the displayed start and end times will differ from the actual length of the execution time.

Figure 7-22 shows an example of times that are displayed. Note that, in this example, the execution times in both time zones are 20 minutes.

Table 7‒10: Example of a time zone that switches from standard time to daylight saving time
Time zone	Execution start time (scheduled execution start time)	Execution end time (scheduled end time)	Execution time
Time zone that does not use daylight saving time	4/7 1:50:00	4/7 2:10:00	20 minutes
Time zone that uses daylight saving time	4/7 1:50:00	4/7 3:10:00	20 minutes

In this example, the (scheduled) execution start time is displayed in standard time because JP1/AJS3 is operating in standard time at that time. However, the (scheduled) execution end time is displayed in daylight saving time. Therefore, the end time will appear to move forward.

Table 7‒11: Example of a time zone that switches from daylight saving time to standard time
Time zone	Execution start time (scheduled execution start time)	Execution end time (scheduled end time)	Execution time
Time zone that does not use daylight saving time	10/27 0:50:00	10/27 1:10:00	20 minutes
Time zone that uses daylight saving time	10/27 1:50:00	10/27 1:10:00	20 minutes

In this example, the (scheduled) execution start time is displayed in daylight saving time because JP1/AJS3 is operating in daylight saving time at that time. However, the (scheduled) execution end time is displayed in standard time. Therefore, the end time will appear to move backward.

(b) Display of the time zone for an execution schedule

If JP1/AJS3 is operating in a time zone that uses daylight saving time, the time zone might not be displayed correctly for a job or jobnet in the following locations: the Daily Schedule window of JP1/AJS3 - View or the Chart tab in the Dashboard screen of JP1/AJS3 - Web Console. If a day on which daylight saving time starts or ends is displayed in that window or tab, the displayed start time and (scheduled) end time of a job or jobnet differ from their actual times. This is because the actual start time and (scheduled) end time are displayed in standard time or daylight saving time, whereas the execution schedule is displayed in relative time from the base time. To check the actual start time and (scheduled) end time, use the Execution result list in the Daily Schedule window or the List tab in the Dashboard screen.

The following shows examples of displayed times based on Figure 7-22. In the following examples, the flow of time is divided into hours, with each one-hour period identified by a number, called an index, for convenience.

■ When standard time changes to daylight saving time

The following table shows the relationship between indexes and displayed times for time zones that use or do not use daylight saving time. In the time zone using daylight saving time, the times for jobs and jobnets executed after 3:00 appear as one hour behind the actual execution times.

Table 7‒12: Relationship between the indexes and displayed times when standard time changes to daylight saving time
Time zone	Index
Time zone	0	1	2	3	...
Time zone that does not use daylight saving time	0:00:00 to 0:59:59	1:00:00 to 1:59:59	2:00:00 to 2:59:59	3:00:00 to 3:59:59	...
Time zone that uses daylight saving time	0:00:00 to 0:59:59^#1	1:00:00 to 1:59:59^#1	3:00:00 to 3:59:59^#2	4:00:00 to 4:59:59^#2	...

#1: Time displayed in standard time
#2: Time displayed in daylight saving time

The following figure shows an example of the relationship between execution schedules and displayed times in a case where standard time changes to daylight saving time.

[Figure]

■ In a case where daylight saving time changes to standard time

The following table shows the relationship between indexes and displayed times for time zones that use or do not use daylight saving time. In the time zone using daylight saving time, the times for jobs and jobnets executed after 1:00 (after switchover to standard time) appear as one hour ahead of their actual execution times.

Table 7‒13: Relationship between the indexes and displayed times when daylight saving time changes to standard time
Time zone	Index
Time zone	0	1	2	3	...
Time zone that does not use daylight saving time	0:00:00 to 0:59:59	1:00:00 to 1:59:59	2:00:00 to 2:59:59	3:00:00 to 3:59:59	...
Time zone that uses daylight saving time	0:00:00 to 0:59:59^#2	1:00:00 to 1:59:59^#2	1:00:00 to 1:59:59^#1	2:00:00 to 2:59:59^#1	...

#1: Time displayed in standard time
#2: Time displayed in daylight saving time

The following figure shows an example of the relationship between execution schedules and displayed times in a case where daylight saving time changes to standard time.

[Figure]

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