code: function (format) {
  		var chars = '';
  		var literal = false;
  		// Check whether a format character is doubled
  		var lookAhead = function(match) {
  			var matches = (iFormat + 1 < format.length && format.charAt(iFormat + 1) == match);
  			if (matches)
  				iFormat++;
  			return matches;
  		};
  		for (var iFormat = 0; iFormat < format.length; iFormat++)
  			if (literal)
  				if (format.charAt(iFormat) == "'" && !lookAhead("'"))
  					literal = false;
  				else
  					chars += format.charAt(iFormat);
  			else
  				switch (format.charAt(iFormat)) {
  					case 'd': case 'm': case 'y': case '@':
  						chars += '0123456789';
  						break;
  					case 'D': case 'M':
  						return null; // Accept anything
  					case "'":
  						if (lookAhead("'"))
  							chars += "'";
  						else
  							literal = true;
  						break;
  					default:
  						chars += format.charAt(iFormat);
  				}
  		return chars;
  	}
docs: /* Extract all possible characters from the date format.