Round Minute Down to Nearest Quarter Hour

Round minute down to nearest quarter hour

Your full function would be something like this...

function roundToQuarterHour($timestring) {
    $minutes = date('i', strtotime($timestring));
    return $minutes - ($minutes % 15);
}

php: round minutes up to the nearest quarter hour, then do more

Try:

$units = ceil($minutes / 15) 

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

Given that you have hours and minutes in variables (if you don't you can get them from the Date instance anyway by using Date instance functions):

var m = (parseInt((minutes + 7.5)/15) * 15) % 60;
var h = minutes > 52 ? (hours === 23 ? 0 : ++hours) : hours;

minutes can as well be calculated by using Math.round():

var m = (Math.round(minutes/15) * 15) % 60;

or doing it in a more javascript-sophisticated expression without any functions:

var m = (((minutes + 7.5)/15 | 0) * 15) % 60;
var h = ((((minutes/105) + .5) | 0) + hours) % 24;

You can check the jsPerf test that shows Math.round() is the slowest of the three while mainly the last one being the fastest as it's just an expression without any function calls (no function call overhead i.e. stack manipulation, although native functions may be treated differently in Javascript VM).
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make function round up to nearest quarter hour

How about this:

new Date(Math.ceil(new Date().getTime()/900000)*900000);

Explanation: new Date().getTime() returns the current time in the form of a unix timestamp (i.e. the number of milliseconds since 1970-01-01 00:00 UTC), which we round up to the nearest multiple of 900000 (i.e. the number of milliseconds in a quarter-hour) with the help of Math.ceil.

Edit: If you want to apply this to intervals other than 15 minutes, you can do it like that (e.g. for 30 minutes):

var interval = 30 * 60 * 1000; // 30 minutes in milliseconds
new Date(Math.ceil(new Date().getTime()/interval)*interval);

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

Rounding

You will need to use modulo to truncate the quarter hour:

Date whateverDateYouWant = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(whateverDateYouWant);

int unroundedMinutes = calendar.get(Calendar.MINUTE);
int mod = unroundedMinutes % 15;
calendar.add(Calendar.MINUTE, mod < 8 ? -mod : (15-mod));

As pointed out by EJP, this is also OK (replacement for the last line, only valid if the calendar is lenient):

calendar.set(Calendar.MINUTE, unroundedMinutes + mod);

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Improvements

If you want to be exact, you will also have to truncate the smaller fields:

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

You can also use DateUtils.truncate() from Apache Commons / Lang to do this:

calendar = DateUtils.truncate(calendar, Calendar.MINUTE);

How do I round datetime column to nearest quarter hour

Assuming that your series is made up of datetime objects, You need to use Series.apply . Example -

import datetime
df['<column>'] = df['<column>'].apply(lambda dt: datetime.datetime(dt.year, dt.month, dt.day, dt.hour,15*(dt.minute // 15)))

The above example to always round to the previous quarter hour (behavior similar to floor function).

EDIT

To round to the correct quarter hour (as in , if its 7 mins 30 seconds past previous quarter, to show the next quarter) . We can use the below example -

import datetime
df['<column>'] = df['<column>'].apply(lambda dt: datetime.datetime(dt.year, dt.month, dt.day, dt.hour,15*round((float(dt.minute) + float(dt.second)/60) / 15)))

The above would only take the latest seconds into consideration , if you want the millisecond/microsecond into consideration , you can add that to the above equation as - (float(dt.minute) + float(dt.second)/60 + float(dt.microsecond)/60000000)

c# - rounding time values down to the nearest quarter hour

x = x - (x % 15) would be a solution that doesn't rely on integer division.

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