In the Garden of the Dead

The Square Lake Cemetery was established in 1866, but the majority of the plots seem to be from the last ten years. In fact, I don't think I saw anything more than 100 years old. There are lots of empty plots held in reserve, like an executive parking place with somebody's name on the placard. New cemeteries have a weird feel to them. More so when there's a band next door playing Earth Wind & Fire.

Calling out to LJ hivemind

If I'm trying to find out when the high holy days were in 1873, is there a formula or a website that can help me? My google fu is weak and has not helped me.