During or for?

We use during to say when something happens, if it happens in or over a period of time. We use for to talk about the length of time something lasts.

Compare

They went to Florida during the winter.	They went at one point in the winter.
They went to Florida for the winter.	They went from the beginning to the end of the winter.

She phoned me during the week to tell me that she was getting married. (referring to a point in the week)

We were in the cinema for three and a half hours.

Not: … during three and a half hours.

Our flight to New York was delayed for seven hours.

Not: … during seven hours.

We went to Italy for a week.

Not: … during a week.

We can also use for to refer to public holidays and seasons:

He always goes to his mother’s house for New Year.

Not: … during New Year.