For vs. during

It happened during the last two weeks - it happened once in the last two weeks.

It happened for the last two weeks - it started two weeks ago and continued until now(/or you left now).

Thank you Dave Phillip.

What if I say:

I was the doorkeeper of the house for the last two week of my stay in London during which my friend was on holday.

Does 'for' above mean I took care of the house for a duration of two weeks and starting two weeks before I left London?

Does 'during which' above correct? Or it should be 'for which' to in

I don't quite understand 'doorkeeper'. I think you mean that you were in charge of the premises while he was away. - Key holder (one word or two there is some debate about that I can't answer).

I was the keyholder of my friend's house for the last two weeks stay in London. During which my friend was away on holiday.

For you were in charge of for the whole 2 weeks. During you

Dave is correct. "During" indicates preterite, or a past event that occurred and ended in a concrete amount of time. "For" indicated the imperfect tense, an ongoing past event.

Thanks Dave for your explanation and thanks Anon for the additional info.

The way I understand your explanation 'for' in the given context indicates an action which happened continuously for a whole period, whereas 'during' indicates an action which probably happened once or continuously for a period within a given period. I hope I've got the right idea.

Could you please confir

Yes, you've got it.

Thank you so much. Great help!