The tag is present in Lintian version 2.104.232. That is the most recent version we know about.
The date format in the latest changelog entry file appears to be invalid.
Dates should use the following format (compatible and with the same semantics of RFC 2822 and RFC 5322):
day-of-week, dd month yyyy hh:mm:ss +zzzz
To avoid problems like this, consider using a tool like dch(1) or date(1) to generate the date. Example:
$ date -R -ud '2013-11-05 23:59:59' Tue, 05 Nov 2013 23:59:59 +0000
Refer to Debian Policy Manual section 4.4 for details.