Checking my last day of health coverage - what worked for you?

I was told my coverage ends on my last day, but the letter says the end of the month. There are 15 people counting on me, so I am trying to be careful. I have an appointment next week. What should I do about appointments?

Dental and vision sometimes end on a different date from medical. Mine did.

Keep a copy of any coverage confirmation in case of later disputes.