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

Maybe you can use an utility library for manipulating Dates, here for example you have a round method which can be useful for you:

http://commons.apache.org/lang/api-2.4/org/apache/commons/lang/time/DateUtils.html#round%28java.util.Calendar,%20int%29

Here an example in code:

    FastDateFormat formatter = DateFormatUtils.ISO_DATETIME_TIME_ZONE_FORMAT;

    Date now = new Date();
    System.out.println("now = " + formatter.format(now));       

    // Get nearest second
    Date nearestSecond = DateUtils.round(now, Calendar.SECOND);
    System.out.println("nearestSecond = " + formatter.format(nearestSecond));

    // Get nearest minute
    Date nearestMinute = DateUtils.round(now, Calendar.MINUTE);
    System.out.println("nearestMinute = " + formatter.format(nearestMinute));

    // Get nearest hour
    Date nearestHour   = DateUtils.round(now, Calendar.HOUR);
    System.out.println("nearestHour = " + formatter.format(nearestHour));

Answer 2

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)

Answer 3

public static Date getCurrentDateTimeWithQuarterRounding() {
    final Calendar calendar = new GregorianCalendar();
    calendar.setTime(new Date());
    calendar.set(Calendar.MILLISECOND, 0);
    calendar.set(Calendar.SECOND, 0);
    final int minutes = calendar.get(Calendar.MINUTE);

    if (minutes < 15) {
        calendar.set(Calendar.MINUTE, 0);
    } else if (minutes >= 45) {
        calendar.set(Calendar.MINUTE, 45);
    } else if (minutes < 30) {
        calendar.set(Calendar.MINUTE, 15);
    } else {
        calendar.set(Calendar.MINUTE, 30);
    }

    return calendar.getTime();
}

Answer 4

One more alternate approach using java Instant api.

Instant instant =  Instant.now();
int intervalInMinutes = 10;
instant.truncatedTo(ChronoUnit.MINUTES).minus(instant.atZone(ZoneId.of("UTC")).getMinute() % (1* intervalInMinutes),ChronoUnit.MINUTES);

Answer 5

Wonderful post, thank you so much guys! It was exactly what I needed :)

Here's my code based on jour work.

My usecase is "Given it's 11:47 am, I want to set two dates symbolizing the current 5-minutes frame : 11:45 am and 11:50 am"

            Calendar calendar = Calendar.getInstance();
            calendar.set(Calendar.SECOND, 0);
            calendar.set(Calendar.MILLISECOND, 0);

            int modulo = calendar.get(Calendar.MINUTE) % 5;
            if(modulo > 0) {

                calendar.add(Calendar.MINUTE, -modulo);
            }

            myObject.setStartDate(calendar.getTime());

            calendar.add(Calendar.MINUTE, 5);
            myObject.setDueDate(calendar.getTime()); 

Answer 6

It's simple, find the number of quaters since 1970 as double, round it and multiply by 15 minutes:

long timeMs = System.System.currentTimeMillis();

long roundedtimeMs = Math.round( (double)( (double)timeMs/(double)(15*60*1000) ) ) * (15*60*1000) );

Set your Date or Calendar object with that.