Daylight saving time and blackout periods
Blackout periods for synthetic transaction monitoring are used to disable monitoring and notifications, such as for maintenance or troubleshooting. In Execution Plans, you can set blackout periods to occur regularly, on a weekly schedule, or you can set blackout periods to occur once.
Each blackout period can be set only within a 24-hour day, from midnight to midnight. This means that for a blackout that spans midnight, you need to set two blackout periods. For example, for a blackout from 23:00, until 1:00, you set one blackout from 23:00 until midnight, and another from midnight until 1:00.
For every execution of an Execution Plan, before the execution begins, the TEA Agent checks if the Execution Plan is in a defined blackout period. If it is, the TEA Agent skips the execution.
Many countries and regions employ daylight saving time (DST), also called summer time, which is the practice of advancing clocks in spring to add more daylight hours in the evening. In autumn, clocks are adjusted back an hour, to return to the region's standard time. Changes to DST can affect the time of the blackout period, so that the start time of a blackout period for an Execution Plan can vary one hour when the clocks are adjusted. This discrepancy is different based on whether your blackout periods are configured to run on UTC time or the TEA Agent's local time.
- If you set a blackout period by UTC time, DST changes mean a perceived change in the local time that the blackout occurs.
For example, let's say you set a blackout period in UTC time that corresponds to 23:00-midnight. When you change the local clocks to DST, the blackout period now corresponds to midnight-1:00 because the UTC time itself is not affected by the clock change. The duration of the blackout period does not change, but the perceived local time when it occurs does.
- Conversely, if you set your blackout periods by TEA Agent local time, in DST blackouts occur at the same time locally, but they may be affected by the time change.
For example, let's say you set one blackout period from 23:00 until midnight in your local time, and you set another one from midnight until 1:00 in the morning, thus creating a two-hour blackout period in the middle of the night. Assuming that the change to DST occurs at midnight and the change back to standard occurs at 1:00, if you are using TEA Agent local time to set your blackouts the change to and from DST has the following effects:
- On the change to DST, your actual blackout is only one hour, 23:00-midnight: and then midnight becomes 1:00, so the second defined hour doesn't have any effect.
- On the change from DST back to standard time your actual blackout is three hours: 23:00-midnight, and then midnight-1:00 covers a two-hour period (one hour before the clock change, and one hour after).
Blackout settings for synthetic monitoring