The TagName is whatever you want to call the branch.

Identifier is an identifier for the node to be tagged. The identifier can be one of the following:

1. A branch name: Tag the most recent commit on this branch
2. An SHA1 identifier: Tag the commit with this SHA1 identifier
3. A datestamp (YYYY-MM-DD): Tag the commit just previous to this datestamp
4. A timestamp (YYYY-MM-DD HH:MM:SS): Tag the commit just previous to this timestamp

        # Tag the current tip of the trunk as release_1.0
        $ fossil add tag release_1.0 trunk

        # Tag the last commit on December 15 as beta_release_1
        $ fossil add tag beta_release_1 2016-12-16