dlowe-net/local-time — pull request #23 by kanru (2014-05-06 15:44:29+00:00)
Title: Change +rfc-1123-format+ to use numeric timezone indicators

RFC-1123 section 5.2.14 writes

> "There is a strong trend towards the use of numeric timezone
indicators, and implementations SHOULD use numeric timezones
instead of timezone names."

RFC-822 section 5.1 writes the syntax of timezone

```
zone = "UT" / "GMT" ; Universal Time
; North American : UT
/ "EST" / "EDT" ; Eastern: - 5/ - 4
/ "CST" / "CDT" ; Central: - 6/ - 5
/ "MST" / "MDT" ; Mountain: - 7/ - 6
/ "PST" / "PDT" ; Pacific: - 8/ - 7
/ 1ALPHA ; Military: Z = UT;
; A:-1; (J not used)
; M:-12; N:+1; Y:+12
/ ( ("+" / "-") 4DIGIT ) ; Local differential
; hours+min. (HHMM)
```

Which I feel using the numeric is the way to go. It's always valid
that we don't have to worry about if the timezone abbreviation is in
the allowed list.