are you saying it's manually triggered when it doesn't tick at scheduled time of maybe 1600 UTC?
More complicated than that.
The tick is a process, not an event, so across the populated galaxy it can take about 20-60 minutes to complete. If you were logged in before the tick, your client may also be caching some data locally, so you might not
see the tick in some data for another couple of hours.
The tick is supposed to start 24 hours after the start of the previous one, which it usually does, but if there's any delays to the tick then the next one will be later, and then that will be the new scheduled time. So it tends to slowly rotate around the clock, with periods of greater or lesser stability: at the moment it's reasonably stable and has been starting at about 1600 for a while, whereas at other times it can slip by an hour or two a day.
On major version releases it will sometimes be reset to 1200 UTC, or sometimes allowed to continue at its previous time.