The tag is present in Lintian version 2.109.24. That is the most recent version we know about.
This package appears to be the first packaging of a new upstream software package (there is only one changelog entry and the Debian revision is 1) and uses a date-based versioning scheme such as YYYYMMDD-1.
Packages using date-based version numbering should use a "0~" prefix (eg. 0~20201612-1 or similar) to avoid having to introduce an epoch if upstream starts tagging releases in a more conventional manner.