"You must come back home before it gets dark"

[LeTyan]

Hi,

"You must come back home before it gets dark."

I am always under the impression that the word "before" can only be used in past tense. Therefore I am not sure if "before" is proper here.
If not, how do we paraphrase this sentence in the right way?

Thanks!

 

[MikeNewYork]

The original sentence is fine. "Before" can be used with future times.

I will pay you back before the deadline.
I will be in Chicago before I fly to Philadelphia.
I will be in bed before midnight.

 

[LeTyan]

The original sentence is fine. "Before" can be used with future times.

I will pay you back before the deadline.
I will be in Chicago before I fly to Philadelphia.
I will be in bed before midnight.

Thank you Mike! (I don't know why the "like" option to like someone's post disappeared. Maybe the sever is acting out for some reason)

So it's both Okay to say "All the homework must be turned in by/before Friday. Is that right?

 

[5jj]

"All the homework must be turned in by/before Friday."

Fine, though 'by' allows handing in on Friday; 'before' doesn't.