alignDateTime function
Rounds down or up a DateTime object using a Duration object.
If roundUp
is true, the result is rounded up, otherwise it's rounded down.
If the duration is a multiple of days, the result will be aligned at
the day mark in the timezone of the source datetime.
Implementation
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;
}