Quick answer
Check whether special-day provisions override the regular schedule and whether odd/even years are defined.
Do now
Compare the order with the school calendar. Identify exact start and end times, transportation, and advance notice requirements. Propose a specific written clarification through a permitted channel before the disputed date.
Watch for
An informal pattern may not override the written order. If the order is ambiguous, seek clarification rather than using the child as the messenger or making competing travel plans.
Official sources
NJ Courts — FD modification application packet, NY Courts — Custody and Visitation, DC Courts — Family Court Self-Help Center.