I think this is old news, but I was searching for this exact phrase and not seeing much on the Bugs forum.

The "Upcoming Border Engagement(s)" mission shows a countdown to a time that looks like UTC plus 1 hour and some change, given the countdown.

For example, right now it says "Begin at 17:00", but shows a countdown of (03:00). It's like 15:50Z now.

The countdown timer finished and there's no new border skirmish. Maybe there will be one at 1700Z?

Now a large skirmish appeared at 1600Z.

Is there something applying daylight savings time offset to the "Upcoming Border Engagement(s)" mission?

That's odd, we'll take a look.