How to round time to the nearest quarter hour in java?

Question

Given today\'s time e.g. 2:24PM, how do I get it to round to 2:30PM?

Similarly if the time was 2:17PM, how do I get it to round to 2:15PM?

Answer 1

With the answer above you end up with all kind of interesting code to handle overflows to hours, days etc.

I would use the time in ms since the epoch.

add 7.5minutes or 7.5x60x1000 = 450000

and truncate to a multiple of 900000

new Date(900000 * ((date.getTime() + 450000) / 900000))

This works, because the time where the ms time starts happens to be 00:00:00. And since all time zones in the world change in 15min steps, this does not affect rounding to quarters.

(Oops, I had a 0 too much and forgot some important parentheses : it is still too early)