Similar to a budget, the school calendar depicts a system's priorities.
It's essential to make the calendar a year ahead and stick to that calendar as much as possible.
In fact, it would be a good idea to pass out the school calendar at the end of the previous year in move-up letters and schedules so that educators, parents, administrators, students, and citizens can prepare.
Our arts department does a good job with this. They typically have all the arts events on the calendar by June. This helps a lot with planning.
Other events that could be planned ahead include sports banquets, cultural events, cultural enrichment events and more. For example if you'd like to have educators attend any weekend events, it's good to have those events listed with lead time. It may also be good for educators to have some voice over when those events occur too since they can't give up every weekend, but most educators are willing to attend a number of weekend events particularly if those events support their students. For example, next year I'd like to attend the Chinese Lunar New Year event, Culture Celebration, and perhaps the welcoming picnic--lead time would help a lot with regard to planning to attend those events.
Whatever the calendar process, it's good to make that process transparent and inclusive so that educators, family members, students, and the community are aware of the process, planning, calendar events, and where the calendar can be easily accessed online.