Japan of course! Central post offices (and major secondary ones) in most cities will be open 7 days a week but those in smaller cities may have limited hours on Sundays.
Sunday in US is a mixed bag…the service window is closed and maybe the lobby area where po boxes are located. They deliver parcels sometimes, but not letters. You can buy stamps at big grocery stores.
In Poland there are post offices open on Saturdays, though less and less.
In my city there was one open 24/7 but this has changed recently. Not sure if it still works on Sundays but with shorter hours, or if Sundays have been discontinued.
On the main USPS.com website, you can go to “Locations” on the top or hover over “Quick Tools” and then click on “Find USPS Locations” and under the two search boxes (Find a Location & Location Type), there are some filters. One of those filters that you can click on is “Sunday Hours”
USPS:
Until the 1990’s collection services were 365/7 in cities and larger towns (and even some small ones) and mail would be postmarked and processed as any other day. Big cities would have at least one post office open 365/24/7 with full counter service. New York City’s GPO was like that until about the early 2000’s. Now it has limited Sunday counter service hours and nothing is processed until the next business day. I believe the Church Street and Grand Central offices also had counter service 365 days a year though not 24 hours but late into the night like midnight, if I remember correctly. That ended about 20 years ago and there is no counter service at all Sundays and holidays. The working day hours are also much shorter. Some small branches in NYC no longer open on Saturdays. Also 24 hour PO Box access appears to have been discontinued except at the GPO (aka the Farley building and now Moynihan Train Station).
I have also noticed some small town post offices are closed on Saturdays now. Also some collection boxes have no Saturday clearance listed even in a big city like New York.
The bigger “major” post offices are open usually around 9am to 5pm Monday to Friday,
but you can find smaller post offices open until like 9pm if they are located inside a newsagent for example on the weekends as well.
Hello! I live in Russia, in a small Siberian city with a population of just over 40 thousand people. We have only two post offices. One of them is closed on Sunday. But the second post office is open every day, seven days a week (on Sunday they have a short day, until 16:00). But don’t worry about the employees, they still have two days off. They just work on a shift schedule.
In Austria (some?) post offices are open on Saturdays until noon. They are not open on Sundays, except, I think, the main post office (unless that has changed, my knowledge is a bit “vintage”! ).
In Switzerland, most Post Offices are open reduced hours on Saturday. Some (very few) open on Sundays (Without looking everywhere, I found at least one in Zürich.)
In my experience most UK post offices that are inside stores eg newsagent and grocery, are open at least till midday on Saturday. As are many standalone Postoffices like the one in my village.
My guess is that the timing of closure may depend on the time of the last Saturday collection.
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