Time event triggering behavior

Document ID : KB000093183
Last Modified Date : 27/04/2018
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This article explains the behavior of time event with example:

I have a time event with info specified on the Calendar tab. For example, it says only trigger between 21:05 and 04:00. I activate the time event right now - and my expectation is that it will start triggering things at 21:05. However, when I go to the Details of the time event I see 2 things that I consider odd or unexpected:

1 - The Check Count is 1. Why would it have already checked? The conditions say don't start doing anything until 21:05 so wouldn't 21:05 be the first check?
2 - The Next Check value is 21:06:29. ???? Why on earth - before it even starts for the first time would it already be off by a minute and a half?
To answer the questions, please first be informed about the nature of time event:
Time event is created for the purpose of periodically check if the CURRENT time is eligible for a set of predefined calendar conditions. So it's different from Schedule or recursive executions where users define exact/expected start times.
The check for time event start ticking from the moment of activation.

1 - For the first check count: Please notice that there is the First Activation settings, if you choose Immediately, then the event will proceed a check immediately at the time of activation which appeared to you as the first check count.
Interval activation settings for time event

2 - Next check: Time event will continue to check at moments that have n times of intervals difference from the time of activation, so in your case, for example, we can understand that if interval was set for 10 minutes (and check count was 1) then probably the first check was at 20:56:29 (10 minutes earlier). Please remember that time event check if current time is within the calendar definition yet, NOT check at the start time of calendar period.
Additional Information:
Defining TIME Event Object: