For what it's worth... Number 2 has my vote. The way I see it : - Number 1 with 'for' would work, but it would have to be a period of time : '...on leave for a day or two'. - Number 3 with 'during' suggests a period of time, but a longer one : '... on leave during Easter holiday'.
1. You can't be on leave for a date; "for" has to be followed by a complement stating the length of time. It could be "for one day", "for 24 hours", "for 2 days", ...
2. "on" is OK
3. You can't use "during" before a date either. You have to use it before the noun that qualifies the length of time. It could be "during the week-end", "during the Christmas holidays", "during