hours property
Moves the thumbs based on hours.
For example, if min is DateTime(2000, 01, 01, 05) and
max is DateTime(2006, 01, 01, 20) and SliderDuration(hours: 5) then
the thumb will get moved at DateTime(2000, 01, 01, 05),
DateTime(2000, 01, 01, 11), DateTime(2000, 01, 01, 16),
and DateTime(2000, 01, 01, 20).
Implementation
final int hours;