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# Excel/Calculating Months Excel 2007

Question
I have 2 variables; Effective Date in Column A & Duration in Column B.
I have a project that starts 1/1/2013 and has a duration of 36 months:
Column C needs to show 12 for the active months in Calendar Year 13.
Column D needs to show 12 for the active months in Calendar Year 14.
Column E needs to show 12 for the active months in Calendar Year 15.

My projects will never go over 36 months, but could be less i.e.:

I have a project that starts 6/1/2013 and runs for 18 months.
Column C should show 7 for the active months in Calendar Year 13.
Column D should show 11 for the active months in Calendar Year 14.
Column E would be zero.

What would the formulas be in Column C, D, & E for my many projects with many Effective Dates and durations?

Gene
If I am understanding your criteria parameters your formulas would look like this--

cell C3  IF(12-MONTH(A3)+1<12,12-MONTH(A3)+1,12)
cell D3  IF(B3-C3>=12,12,B3-C3)
cell E3  IF(B3-C3-D3>=12,12,+B3-C3-D3)
cell F3  IF(B3-C3-D3-E3>=12,12,+B3-C3-D3-E3)

You should be able to copy and paste these directly to your sheet.
A caution--the formula MONTH(A3) will yield the month of the date that is within the cell A3, so if the date is 6/1/13 the month is 6, if the date is 5/31/13 the month is 5, so in this formula one day can make a one month difference in the way it calculates.  If your start dates are all on the first of a month then all is okay, but if they are not then a problem could arise.

Hope this works for you.

Richard
Florida
USA
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#### Richard Roberts

##### Expertise

Can assist you in most areas of Excel, have been working with it for about 15 years in many types of applications, but primarily in financial and accounting applications. I am a CPA and many client or client problems have necessitated the use of excel. I am not an expert in charting, macros, or pivot tables.

##### Experience

Have been working with Excel for about 20 years primarily in accounting and financial areas.

Education/Credentials
BA, Certified Public Accountant