What the count looks like
Of the 567 restaurants here, 186 set their closing day by weekday. Tallied out: Sunday 61, Monday 47, Tuesday 47, Wednesday 38, Thursday 18 — and Saturday 3, Friday 1.
Almost nothing closes at the weekend. Friday and Saturday are when restaurants earn. That is convenient for visitors: if your Nagoya days are a weekend, essentially everything is open.
The risk is Monday — and, less obviously, Sunday
Monday makes intuitive sense. After a worked weekend, the owner-run places take it off.
Sunday is the one people miss. At 61 shops it is the single biggest day, and the closures skew towards old places that run on local regulars — which is to say, exactly the kind of restaurant you came to Nagoya for. If Sunday is your only night, plan for the second choice rather than the first.
176 shops never close
On the other side, 176 restaurants keep no regular closing day at all — 31% of the total. Chains, station-building restaurants and the larger izakaya sit here.
So there is no day when "everything in Nagoya is shut." What closes is a specific shop, not the city. Each dish page lets you slide across to another restaurant serving the same thing, which is what that page is for.
And 66 close irregularly
Sixty-six shops set no weekday at all and decide week by week. Another 60 fall under "other," and 79 have no data recorded.
That layer can only be confirmed directly. It is why every shop page carries a phone number and a link to the official site. On a day when you are travelling out of the city, or when one restaurant is the entire point, call ahead.
Public holidays run on different rules
Around public holidays the weekday pattern breaks. If a Monday is a holiday, most shops open and take Tuesday instead. Conversely, the night before a holiday runs as busy as a Friday.
New Year and the Obon week follow neither pattern. Independent shops can close for the better part of a week, leaving only chains. If you are visiting then, check the official site of anywhere you have your heart set on.
So build the itinerary this way
Put the restaurants you most want on Friday and Saturday. They will almost certainly be open.
Give Sunday and Monday to the never-closing shops, the chains and the larger izakaya. Nagoya Station and Sakae are thick with that layer, so shifting a Sunday night there rarely fails. Closing days are printed on every shop page — before you fix the plan, check the one place you refuse to miss.