"They study in the afternoon."
Translation:Zij studeren in de middag.
Good question. I always thought middag meant afternoon, but according to my dictionaries, middag does mean midday or noon. As a native Dutch speaker, Zij studeren in de middag doesn't sound right. A better sentence would have been: Zij studeren 's middags (most common) or, Zij studeren namiddag, both of which mean in the afternoon.
"Middag" can mean both "noon" and "afternoon". I think there is quite some variation even amongst the Dutch/Flemish themselves in how we use these sort of time words, and what these words cover/mean to us exactly. So I guess as a learner, you will have to be prepared to see some vague/flexible use of these terms here and there (sorry!).
To me for example (I'm from South Holland), "middag" means "afternoon" first and foremost (covering the whole period from 12/1PM to 5/6PM). It would take some context for me to interpret it as just "noon". Therefore, unlike Dutchesse, I think "in de middag" sounds fine and I actually use that a lot myself. "Na de middag" would be after 5PM-ish for me (literally "after the afternoon"), and is something I have never heard used to mean "in the afternoon" before (so I learnt something new today too :D). For "noon" I mostly just use "12 uur", or sometimes "noen" or even "het middaguur" (e.g. "around noon" would be "rond het middaguur").
For clarification, I based my response on what the Dutch-English dictionaries said, and I found that the meaning of "middag" from an English standpoint means noon or midday or exactly 12 o'clock. See here: https://www.merriam-webster.com/dictionary/noon. To me the Dutch word middag has also always meant the afternoon (meaning the period after 12 o'clock up until maybe 6 pm). However, I did some more research, and the original meaning of the Dutch middag also meant 12 o'clock, according to Taaladvies: http://taaladvies.net/taal/advies/vraag/878/voormiddag_namiddag, specifically this paragraph: "De oorspronkelijke betekenis van middag is letterlijk 'het midden van de dag', dus 'middaguur' (12 uur)." (copied from the paragraph under Toelichting). So, even though the meaning of middag has changed in the Dutch language over the years, apparently Dutch-English dictionaries still consider its meaning to be noon or midday, both of which mean twelve o'clock.
Exactly! I live in Flanders and here middag is mostly still really noon, so from 11.30 to 14.00, not the afternoon (from 14.00 to 17.00 give or take).
But even this depends on where in Flanders you are and how old you are. My aunt uses 'noen' for 'noon' and middag for the afternoon, even though they also use achternoen for namiddag.
So if you want to be sure, just ask what time you have to be there. It's rather annoying of you consider middag to end at 14.00 and people show up at 16.00 saying they are right on time... ;) (a thing that frequently happens when your in-laws are dutch and you are flemish)