Regular expression for UTC date.
npm install regex-utc-date
var regex = require('regex-utc-date');
regex().test('Sun, 07 Dec 2014 09:44:50 GMT');
// => true
var match = regex().exec('Sun, 07 Dec 2014 09:44:50 GMT');
match[0] // => 'Sun, 07 Dec 2014 09:44:50 GMT'
match[1] // => 'Sun'
match[2] // => '07'
match[3] // => 'Dec'
match[4] // => '2014'
match[5] // => '09:44:50'
match[6] // => '09'
match[7] // => '44'
match[8] // => '50'