Well, it might have been easy, but it's got several gotchas (in
both Python and C), including:
- The zone field (%Z) only corresponds for the GMT and UT timezones,
which are obsolete (see RFC 2822). There is no support for
the recommended +/-time-offset form.
- The day-of-week (%a) and month (%b) fields in strptime and
strftime are subject to the process's locale, whereas the RFC
time forms are not. Those are hardwired to names that happen
to correspond to the C, POSIX, and probably most of the en_*
locales, but not to others that would be used by billions of
people. Thus anyone using your program who doesn't happen to
reside in one of the English-speaking countries (or does and
is using a native locale) is likely to encounter problems when
using your program.
- The day-of-week field is optional.
- Comments are allowed (but deprecated) in the whitespace fields
of the time format. (On the other hand, I've never seen this
is normal e-mail.)
I find the use of strptime and strftime difficult enough to manage
with Internet date/times that I restrict my use of them to programs
that are limited to processing date/times. Even then, I then
explicitly set the locale (LC_TIME) to the "C" locale. Otherwise,
I use ad hoc code that explicitly recognizes the RFC-defined forms.
