eslHQ - past progressive

Both are correct. In this case, the action can be seen either as an on-going event around a certain point in time (6pm) - in which case the progressive form is appropriate - or as a finished action- in which case you would use the simple form. Remember that grammar is only a way of expressing meaning - there is nothing which you "can't" say if that form expresses the meaning that you want to convey. The nicest example of this that I know is the word piano - as in the musical instrument. Now - is piano a countable or uncountable noun ? Think about it then scroll down.

And down - keep thinking.

And down a bit more.

You probably decided it was countable, right? As in I bought a piano yesterday / We have 2 pianos at home. OK, now - would it be correct to use it uncountably ? Think about that (yes, I know it's obvious there's a catch, but what would you say to a student who asked you that question? Be honest) OK, if you've thought about it, scroll down ....

And down ....

Keep going....

Right, here's the punchline - Mummy termite to Baby termite : Are you hungry sweetie? Come into the living room and have some piano....
You see, it just depends what you want to "mean". Uncountable nouns are English grammar's way of conveying the idea of a substance. If you regard a piano as a substance rather than a musical instrument, you use the word uncountably. Grammar is a tool for expressing the meaning that we want to express - it obeys us, not vice versa.