^[^+]*$|\+(|0*[0-9]|0*[1-9][0-9]|[1-9][0-9][0-9]|0([1-7][0-9][0-9]|8[0-9][0-9])|0(90[1-9]|9[1-9][0-9])|[1-9][0-9][0-9][0-9]|[0-9][0-9][0-9][0-9][0-9]+)([^0-9]|$)

●入力と結果(✓一致 ❌不一致)
✓ Sat May 24 08:05:44 2014
✓ Tue Mar 28 06:21:47 2017 +
✓ Tue, 26 Jul 2016 23:55:46 -0
✓ Wed, 05 Oct 2016 15:24:09 -0900
✓ Wed, 4 Mar 2015 08:39:08 +09000
✓ Fri, 30 Oct 2015 07:56:41 +00900
✓ Wed, 4 Mar 2015 08:39:08 0900
❌ Wed, 25 Mar 2009 14:18:41 +0900
❌ Tue, 8 Mar 2016 16:11:55 +0900 (JST)
❌ Sat, 24 Jul 2004 03:48:21 +0900<br>