pom: Fix fencepost bugs.
Under some conditions pom would report "waning" and then "full", show
higher percentages than it should, and get confused by DST. Fix.
Before:
2018.01.30: The Moon is Waxing Gibbous (97% of Full) 2018.01.31: The Moon is Waning Gibbous (100% of Full) 2018.02.01: The Moon is Full 2018.02.02: The Moon is Waning Gibbous (98% of Full)
After:
2018.01.30: The Moon is Waxing Gibbous (96% of Full) 2018.01.31: The Moon is Waxing Gibbous (99% of Full) 2018.02.01: The Moon is Full 2018.02.02: The Moon is Waning Gibbous (97% of Full)
PR: 231705
Submitted by: Andrew Gierth
Approved by: allanjude (mentor)
MFC after: 2 weeks
Differential Revision: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=231705