All families develop traditions. One of ours is texting each other (with out without some silliness) at Pi Time - 3:14 in the afternoon. Setting an alarm to warn you of the approach of Pi Time is one of those things that is Not Done, though. You have to encounter it on your own - or, more frequently, notice that it's 3:12 and not allow your attention to wander too much.
If you miss Pi Time, but not by too much, it is acceptable to text at 3:15; or, as Eldest Daughter refers to it, Pi's Overlooked, Unloved Older Brother.
12:34 is also significant, though not nearly as fun as Pi Time.