Does the 402 (g) limit run according to the calendar year in which the plan year ends or the calendar year in which it begins? I intend to set up an Excel file regarding this matter, so I wanted some brainstorming as to how i could go about taking this situation into consideration.

402g limit is applied on a calendar year basis (January 1-December 31), even as to fiscal plan year plans.

in other words, a person could defer 15,500 on Dec 31 , 2008 and 16,500 on January 1, 2009 (if you had such a payroll system) and still be ok for a plan year beginning 2008 and ending 2009.
what is important is what the total on all W-2s for a given year say - no matter how many companies you may work for-
its not just a plan limit, but more importantly an individual limit.

Can an individual have a tax year that is not calendar year? I've never seen it, but is it possible?

Yes but rare.