proof of concept going back in time is diffrent then offsets

I have a questions about time and dates.  I wrote a proof of concept and wanted to see if I my concern is valid.  
With Active Support going forward or back in time seems to not go back a specified amount of time but go back a semantic amount to time.
example.
Time.new(2006,2,28,15,15,10).forward_one_year => 2006 to 2007
not
Time.new(2006,2,28,15,15,10).forward_one_year => + 31557600 sec

This does not account for leap years, or any variations in time.
Should using this library mean going forward 7 years mean a change in the current year by 7 or adding the equivalent of 7 years?

There are gaps in the code where going forward or back wads a year means different things I think.
First off is there a convention I am missing regarding time?  I have not used many other libraries regarding time but the ones I have used mostly add seconds.

Some help understanding this would be great.  I am willing to work on a pull request I just wanted to make sure I am on the right track.