Most all String Theorists describe the ‘additional dimensions’ as dimensions in space.  As we said, multi-dimensional time had been looked at in the past but with little success.  It has only been in the last few years that the mathematics has caught up with the models and physicists have been able to address multi-dimensional Time. 

“Although I feel that D. B. Larson provided the most economical treatment of 3-D time, here's more work exploring the subject, with compelling results:  [comments from the PhysOrgForum] ²⁹

1) “Physicist Xiaodong Chen has a number of papers on the subject of 3-D time:  [extensive mathematics]

2)  “Astronomer William G. Tifft proposed a 3-D time geometry (using Lehto's model) to explain the observed quantization of redshifts.  [large scale at the galactic level]

3)  “Physicist Alexander Mayer proposes that time has a geometry: [Mayer has just released a complete book with illustrations]

4)  “Physicist G. Ziino argued for 3-D time: ("adsabs.harvard.edu On a further argument in support to the conjecture of a three-dimensional time") 
[Notes in brackets are mine] 

Two additional dimensions of time allows for many possibilities, for more degrees of freedom or more importantly, more events and phenomena to occur in the same space at the same time.  If we introduce t2 and t3 into our graphing exercise a more formal definition would go something like this:
    
You’ll be hearing more about 2D & 3D Time in the years ahead and I’m hopeful that we’ll be able to use it as successfully as we have used quantum mechanics in Electronics and other fields of science.  I want to wrap up our discussion into Dimensions, moving from space to magnetic fields. 

Just to the right of you or just overhead is another world.  Do I believe there are multiple universes?  No.  Not multiple universes, just two other worlds; one filled with Principalities, Powers and the other a Kingdom.  [Next up: Fields - see the book]