See the git repository. In particular:

1.06    Also March 2020
    * re-add necessary dependencies to Build.PL

1.05    March 2020
    * add pod-coverage tests and fiddle with the docs as a result
    * require File::Cmp and better log the file contents when the fcmp
      check goes awry
    * switch to Module::Build

1.04 add abs2rel and rel2abs methods, & other cleanups.

1.00 converted module internals to Moo. This changed the return value
     of some of the routines, notably the setters, so those can no
     longer be chained.

0.84 in particular fixed interval2freq to not suck terribly at negative
     intervals, among other fixes and improvements.