"The museum does not open on Mondays."
Translation:El museo no abre los lunes.
rspreng is right -- using "en los lunes" is not accepted. (I know because I answered that way and quickly lost a heart. Ouch!)
I think the reflexive "se" in your sentence would imply the museum opens itself, which wouldn't be correct.
In this case it's "el museo no abre los lunes" because it means that it never opens on monday, that day they are always closed.
"el museo no se abre los lunes" means what SpoolySqueeek said.
That sentence says "The museum is not open on Mondays," which puts the sentence into passive voice.
For days of the week, the articles "el" and "los" (depending on if it is supposed to be plural or singular) can mean "on." It is incorrect to put "en" before days of the week. Therefore, "Voy al banco el lunes" means "I go to the bank on Monday"
Yes, and on a previous question both "el domingo" and "los domingos" were accepted for "on Sunday." Why is "el lunes" not accepted here?
El lunes would not ne accepted here becuase they are refering to more than one monday. You would need los lunes. It is a difference of saying on monday ( singular) and on mondays ( plural )
In your sentence, you're using "open" as an adjective rather than a verb. Though either way we still can't go into the museum on Monday, it is a different sentence.
El museo no esta abierto los lunes--should be correct because it is fundamentally maintaining the meaning of the sentence. And actually the sentence is English is awkward--native English speakers (and I am one) would not say The museum does not open on Monday. They would say--The museum IS not open on Mondays.
"de lunes" would mean "from monday". on mondays = los lunes, on monday = el lunes. es así.
Why not "Los lunes el museo no abre"? In lots of exercises like this I've seen the Spanish translation move the day to the beginning of the sentence.
I tried 'El museo no hace abrir en los lunes'
which translates correctly but isn't the right answer it seems.