How to Round up the Date-Time nearest to 30 min interval in DART (Flutter)? - date

Question

I would like to round DateTime to the nearest 30 mins. Is there rounding mechanism provided in DART?

Answer 1

I had a similar problem today and but it was to clamp to the next 15 mins.
DateTime nearestQuarter(DateTime val) {
return DateTime(val.year, val.month, val.day, val.hour,
15, 30, 45, 60][(val.minute / 15).floor()]);
}
or in your case
DateTime nearestHalf(DateTime val) {
return DateTime(val.year, val.month, val.day, val.hour,
[30, 60][(val.minute / 30).floor()]);
}
I just noticed you said 'nearest half hour'
DateTime nearestHalf(DateTime val) {
return DateTime(val.year, val.month, val.day, val.hour,
[0, 30, 60][(val.minute / 30).round()]);
}
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Answer 2

You can use this function to roundup the time.
DateTime alignDateTime(DateTime dt, Duration alignment,
[bool roundUp = false]) {
assert(alignment >= Duration.zero);
if (alignment == Duration.zero) return dt;
final correction = Duration(
days: 0,
hours: alignment.inDays > 0
? dt.hour
: alignment.inHours > 0
? dt.hour % alignment.inHours
: 0,
minutes: alignment.inHours > 0
? dt.minute
: alignment.inMinutes > 0
? dt.minute % alignment.inMinutes
: 0,
seconds: alignment.inMinutes > 0
? dt.second
: alignment.inSeconds > 0
? dt.second % alignment.inSeconds
: 0,
milliseconds: alignment.inSeconds > 0
? dt.millisecond
: alignment.inMilliseconds > 0
? dt.millisecond % alignment.inMilliseconds
: 0,
microseconds: alignment.inMilliseconds > 0 ? dt.microsecond : 0);
if (correction == Duration.zero) return dt;
final corrected = dt.subtract(correction);
final result = roundUp ? corrected.add(alignment) : corrected;
return result;
}
and then use it the following way
void main() {
DateTime dt = DateTime.now();
var newDate = alignDateTime(dt,Duration(minutes:30));
print(dt); // prints 2022-01-07 15:35:56.288
print(newDate); // prints 2022-01-07 15:30:00.000
}

Answer 3

This function converts a DateTime to the nearest 30 minute mark in a clock. Be warned that this 30 minute mark is obtained with respect to the local time zone of the machine in which this code runs on.
DateTime roundWithin30Minutes(DateTime d) {
final int deltaMinute;
if (d.minute < 15) {
deltaMinute = -d.minute; // go back to zero
} else if (d.minute < 45) {
deltaMinute = 30 - d.minute; // go to 30 minutes
} else {
deltaMinute = 60 - d.minute;
}
return d.add(Duration(
milliseconds: -d.millisecond,
// reset milliseconds to zero
microseconds: -d.microsecond,
// reset microseconds to zero,
seconds: -d.second,
// reset seconds to zero
minutes: deltaMinute));
}
If you are presenting this DateTime in another non local time zone whose offset duration is not a multiple of 30 minutes (eg: Nepal time zone is GMT+5:45) this implementation will not work.

Answer 4

extension DateTimeExt on DateTime {
DateTime get roundMin =>
DateTime(this.year, this.month, this.day, this.hour, () {
if (this.minute <= 15) {
return 0;
} else if (this.minute > 15 && this.minute <= 45) {
return 30;
} else {
return 60;
}
}());
}
You can do It with a simple extension just call it like this
var a = DateTime(2021, 5, 4, 3, 46, 4, 7);
print(a.roundMin);