... instead of resulting in error because of roll-over not being set.
Fallout from
commit 6d424f07701bf26d8fb173563b567d5f097c33e2
CommitDate: Tue May 2 23:12:34 2017 +0200
Replace mouth-painted "inaccurate around leap year" rollover algorithm
that does stricter checking but DateAdd() needs a lax checking
with truncate to last day of month.
Change-Id: I9d6f95ad3ac38257d492019bd621070491e98e76
40c9a129e5