When "Automated" isn't 24/7

So I'm in Tokyo for the week on business. My flight into Narita landed a bit later than planned and so ran to catch the bus to the hotel. Knowing there was a post office/ international ATM near the hotel, I didn't worry about having no Yen with me.

Why the post office? Most of the ATMs in Japan only take domestically issued ATM cards, but the post office is also a bank, and has ATMs. But here's the rub: the ATM closed at 17:00. Silly American, why would you assume an automated banking machine would be open 24/7?

Fortunately I still had a few hundred Yen on my PASMO, and so could take the train to a bank a few stops away...but really.