I think you'll have to define "rebuilt". Is it "95% of residential buildings intact?" Or "all cleaned up, no visible ruins anywhere"? Because if it's the latter, some cities will give you pretty recent dates.

The Frauenkirche was destroyed during the Bombing of Dresden in February of 1945, and reconstruction only finished in 2005.

Going to focus on Britain. For the most part they weren't. When the Luftwaffe levelled say the slums of Landport (bit of Portsmouth around the docks) they weren't about to be rebuilt.

The first rebuilding of homes was in the form of prefabs. Prefabricated houses however they wouldn't be built in areas like Landport. Instead they tended towards new housing estates. Work on those in a more permanent form than prefabs began in the late 40s and continued eh mostly until the early 70s.

Within cities the first rebuilding tended to be commercial as well as new stuff like carparks. You start to see the tower blocks go up in the 60s and again that continues until the early 70s. The Barbican Estate in london is probably the ultimate example. BTW this is one of the reasons brutalist architecture has such a bad reputation in the UK. A lot was put up in the 60s when Britain was really rather short on cash which meant it was often built to low standards by people who didn't really understand reinforced concrete.

Early 70s is probably as good an end date as any. There was some later rebuilding work but it becomes increasingly hard to separate from general construction. By the late 80s you are starting to see some of the post war estates being demolished (Portsdown park went out in 88). If you really want to see the tail end then Southampton's post war development plan (drawn up in 1956) was replaced in 1984. Beyond that other than a few deliberately preserved churches (and Coventry Cathedral) the last bombed out building in the UK is the National Picture Theatre up in Hull.

Can I ask a related question that may be easier to answer? At what point post-war did most European nations' GDP surpass their pre-war GDP?

Warsaw took decades, and there were a couple reasons for that. The first is that the city was effectively destroyed between the Soviet invasion in 1944-45, and the Nazis blowing up everything in the wake of the Warsaw Uprising of 1944. The latter was punishment for the Poles trying to rise up, and came from Hitler himself, though long-term plans were to eventually destroy the city anyways (the seat of the General-Government had been in Krakow since its formation in 1939).

The second issue was that Bolesław Bierut, the post-war leader of Communist Poland, came from the countryside, and hated the urban, Warsaw factions, and everything that it stood for. So he resisted rebuilding the city, especially the historic old city, because of that, and because it clashed with the idea of Communism. It was only when Władysław Gomułka took over that work began to properly restore the city (though some efforts had been made to so since 1945, but they were never fully committed), and rebuild things, most notably the Royal Castle, which was finally completed in 1971. By the 1970s most of Warsaw, or the pre-war aspects of it at least, were rebuilt, with great efforts made to use the same bricks and plans for the buildings, often using paintings and drawings from the pre-war era to match it up.

Edit: I will also note that in comparison, Krakow (which I noted hosted the General-Government), was relatively unscathed throughout the war. Hans Frank, who led the General-Government, set up operations in the Wawel Castle there, the former royal castle, and kept it preserved as a result. There was also no major fighting when the Red Army invaded, so the city and its historic old town were intact.