In my area (in the UK) we regularly use 'for' as a preposition of time. For example, "Could you finish this for 5?" (as in, "Could you finish this by 5?"), a non-native English speaker corrected me and said 'for' can't be used as a preposition of time. I have tried to research this, but it seems like it's something that isn't technically correct. So, I'm wondering if this is just a dialect quirk of where I live, if it's a British English thing, or if this is actually correct but isn't widely taught. If anyone had any solid evidence either way, that'd be great, as I'm really interested.