The same date can be a beginning in one household and a private absence in another.

A single date can be a wedding for one family and a quiet anniversary of loss for another, and neither knows about the other. Public days work the same way: shared celebration on the surface, private difficulty underneath for the people whose calendar was overwritten by something painful. Nobody is doing anything wrong; the dates simply overlap.

When a friend is subdued during a day everyone else finds easy, take it as possible information rather than mood. You do not have to ask what it is. Making a little room, a lighter plan, an unpressured invitation, covers most of what is needed. And if the overlapping date is yours, you are allowed to opt out without explaining.