"(For) the rest of the day" instead of "the rest of the day"

[Rachel Adams]

Can I use "for the rest of the day" or just "the rest of the day"?

"When she doesn't sleep well she is sleepy for the rest of the day

 

[emsr2d2]

In BrE, we'd use "for". I believe that it's commonly omitted in AmE (other users will be able to confirm or not).

In both variants, you need a comma after "well" and a full stop at the end of the sentence.

 

[Yankee]

(AmE) I would expect to use without "for", but not unusual to hear/read with "for".