The shared-reference problem
Households that include grandparents, caregivers, or split-custody arrangements share a coordination problem: every adult needs to know when school is in session, when it is not, when half-days happen, and when the family will be away. Digital calendars are usually the wrong tool for this — too many notifications, too much account complexity, too easy for one adult to be on a different calendar than the others.
Print and mail
The simplest solution is to print the academic-year overview at the start of the school year and mail or hand a copy to every adult who participates in childcare. The printout sits on the grandparents' kitchen counter or the caregiver's binder for the entire year. When it needs to be updated, a single new month gets printed and mailed.
Marking the shared days
Use a colored highlighter to mark the days where extended family is providing care: yellow for grandparent days, green for paid caregiver days, blue for school. The pattern emerges visually after a month or two and makes scheduling adjustments much easier — when a school holiday lands in the middle of a normal weekly pattern, the conflict is visible on the printed calendar weeks in advance.
The split-custody case
For split-custody families, two printed calendars (one for each household) plus a shared single school-year overview is often the most workable pattern. Each parent marks their custody days on their household's printout; the shared overview shows school days, school holidays, and any overlapping commitments. The shared printout is the single source of truth for school events that both parents need to attend.
The annual check-in
The right time to update the shared printable calendar is the first week of August, before the new school year begins. Print the new academic-year overview, hand it out, and walk through any standing patterns (every other Tuesday, every third weekend) so all the participating adults know what the upcoming year looks like.