The Change Calendar in CA Service Management (CA Service Desk Manager) can be used to set recurring change windows. This is useful when there is regular recurring maintenance windows to be scheduled. One window can be set up with one piece of data entry only.
Caution must be exercised if a Change Window occurs during the hours of a Daylight Savings Time change.
Most Daylight Savings Time changes occur on Sunday mornings, between midnight and 3:00 am. For example, the clocks move back from 2:00 am to 1:00 am, or vice versa.
ISSUE If your change window overlaps this time, then you may notice odd results, with the change window moving back or forth by the amount of the time adjustment.
Example: The regular change window is from midnight to 6:00 am on Sunday.
When the Daylight Savings Time change occurs, then looking at the change window for that day may give an odd result such as starting at 11:00 pm on the Saturday before, or starting at 1:00 am or 2:00 am on Sunday.
REASON CA Service Management tracks the day on which a Daylight Savings Change occurs, but does not track the specific hour. All changes are assumed to occur around midnight.
BEST PRACTICE Until an Idea is raised to add this as a feature enhancement (It will be linked here if created), these are the recommended best practices. Pick one approach per Change Window you wish to implement.
1) Avoid Change Windows that overlap with your local Daylight Savings Time changes.
For example, if the time changes always occur on Sundays between midnight and 3:00am, then avoid setting a window which overlaps with this time.
You could set up a Change Window for Monday - Saturday without concern, for example. Or Sunday 4:00am starts.
This is the simplest solution that produces correct results. The cost is at avoiding a good maintenance period for most of the year.
2) Ignore the issue.
If you do not need to strictly observe the Change Window, then the odd day that the calendar is out may be able to be ignored. This would be a site decision as to whether the trade off is worthwhile.
This is the simplest solution, but at times produces incorrect results.
3) Build Change Windows to take account of Daylight Savings Time change.
This option provides accurate results, but at the expense of creating four Change Windows per year instead of one. It also allows Change Windows that overlap with a Daylight Savings Time change.
Ensure CA Service Management is fully patched for the Change Calendar. There is an ITSM 14 patch for the Change Calendar which is in the process of being rolled up into ITSM 17 at the time of this post.
1) Set up a Change Window for one day only, at the START of the Daylight Savings Time change.
This is a non-recurring, one-off Change Window. You may need to tweak the start and end time to produce correct results.
2) Set up a RECURRING Change Window for the period between the start of the Daylight Savings Time change and end day, finishing just before the change.
3) Set up another one-off Change Window that only covers the day of the END of Daylight Savings Time. Again, check it against the calendar to ensure correct hours.
4) Set up another RECURRING Change Window to bring you to just before the start of the next change.
These patches are required for method (3) above to completely work. They do not add "hours" to the Change Calendar Daylight Savings Time. They just enable the existing "days" functionality to work in an overlap period: "Change window displays incorrect start and end time during Daylight Saving Time (DST)"
Thank you for sharing this tip with the community Kyle!
TIP: How to set up Change Calendar to span Daylight Savings Time changes, in Service Management