A date-time unit equal to some number of calendar days.
A calendar day is not considered identical to 24 hours, thus a
DayBased-unit cannot be expressed as a multiple of some TimeBased-unit.
The reason lies in time zone transitions, because of which some days can be 23 or 25 hours. For example, we say that exactly a whole day has passed between
2019-10-28T02:59 in Berlin, despite the fact that the clocks were turned back one hour, so there are, in fact, 25 hours between the two date-times.