URGENT - How does the short tax year calculation determine the "No. of Months in Short Tax Year"

We are frantically trying to determine how the short tax year depreciation calculation works.  We have a similar scenario as a number of others who have posted but there is no real clear answer regarding this subject.  I know that the depreciation calculation is as follows: 

Depreciable Basis * Annual Rate * No. of Months in Short Tax Year /
No. of Months in the Full Tax Year.

Does anyone have any knowledge regarding this calculation, specifically how the the "No. of Months in Short Tax Year" is determined.  Also, has anyone had any experience with adding assets (which qualify for short tax year depreciation) that have a conversion date from a previous period.  Currently the conversion date must be within the same period.  However, we have assets that will not be added into Oracle until October and they will have a conversion date of 9/26/09.  We are holding up our FA close until we can get a clear understanding of this or if there is a work-around.