Use long instead of int for numerous calculations, fixing a number of
date calculation overflow issues.
Obtained from: DragonflyBSD
Git log: 4238ce6f0c6df33ce677ae298b245c62cd60fb43 (only partial)
on March 31 won't take you to March 2 or 3 (now the result will
be the last day of February.)
In general, now stepping by months from the last days of the current
month A will take you to the very last day of the target month B if
B is shorter than A.
The previous version would just step to March 31 and rely on mktime(3)
to correct the date. Despite its simplicity, such way was counter-intuitive
to users and caused pain to shell script writers.
Noticed by: Igor Timkin <ivt at gamma dot ru>
Approved by: brian
MFC after: 2 weeks
things get a bit out-of-phase when we step backwards 1 hour from
between 0:00 and 1:00 on the first of the month following the
transition into Summer time. This is probably actually a bug
in mktime().
PR: 10963
If mktime() fails and 68 < year < 138, assume that the reason is
because of Summer time and adjust up or down according to our
adjusting context by one hour. This assumes that all DSTs are
multiples of 1 hour.
PR: 6223, 17750
statement if blocks[*] when the else could be ambiguous, not defaulting
to int type and removal of some unused variables.
[*] This is explicitly allowed by style(9) when the single statement
spans more than one line.
Reviewed by: obrien, chuckr
