The Post Office on the Grand Concourse closes promptly at 6pm Mon-Fri. That includes all services. I honestly don't think you need an appointment but they do take passport photos here.
I am not sure about the passport process, I know that they only do certain hours when it comes to get a passport, u have to go to the post office on 149th st and grand concourse to find out what hours they specifically do the passport, and if u need a appt to.
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