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.~~