When is changing of the guard

From October through March, it is every hour on the hour. For April through September, it is every half hour.

I believe every half an hour. But if you go when it's colder they change more often.

Every 30 minutes during the Summer, every hour in the Winter starting in October. Although they continue to stand guard throughout the night, the cemetery does close depending on the time of year, so schedule your visit during the cemetery's operating hours.

Every hour.