Add failing test for DST problems.
Use ServiceDate-s when creating ServiceDays ...

... to avoid problems with DST.

With the current +- 24 hour approach there are two 1 hour periods, when
a day is skipped, because there are either only 23 hours in a day (where
+24 hours is the day after), or there are 25 (where +24 hours is the same
day). ServiceDate-s handle DST correctly, which avoids this problem.