Calculate Number of Days and Months to match Excel output

[Astro55]

I'm very new to Alteryx and trying to create a workflow. My data set contains start and end dates for various projects. I need to calculate the number of days and the number of months between the beginning and end dates of each project. 

Issue:
I am getting variances between the Excel and Alteryx calculations. While minor, they can add up to a material impact on my calculations. I figured out how to tweak the Alteryx formula for "number of days" to match my Excel output, but I can't figure out how to do the same for number of months.

Questions:

1. Can you please help me figure out how to get my Alteryx calculation to match my Excel calculation/ output? 

2. Is the "unedited" Alteryx calculation more accurate than my Excel calculation?

Details:

1. Formulas used to calculate the number of days per:
   • Excel: End Date - Start Date + 1
     
     
   • Alteryx: DateTimeDiff([Project End Date_Out],[Project Start Date_Out],'Days') + 1 
                    (Note: The "+1" is to get the Alteryx output to match Excel)
     
     
     
2. Formulas used to calculate the number of months per:
   • Excel: DATEDIF(0,*Number of days*,"M")
     
     
   • Alteryx: DateTimeDiff([Project End Date_Out],[Project Start Date_Out],'Months') 

[binuacs]

@Astro55 I calculated the month difference using the formula DATEDIF(date1, date2,'m') in excel I got the same result as Alteryx, seems to be you are adding 1 to the excel formula result and comparing with Alteryx result. Can you check again? The below red color box I added in excel sheet 

[binuacs]

@Astro55 Is there any reason why you are using FLOOR() function? 

[Astro55]

@binuacs - firstly, thank you SO much for being so responsive!!!

The floor function was suggested by @BRRLL99 . So I tried that to see if it would get me closer to my required solution.

To answer your question about the +1... the difference is due to how the DATEDIF formula is being used:

• The Excel formula in my original workbook: DATEDIF(0,*number of days*,'M')  (i.e., the Excel formula is calculating number of months based on the number of days calculation that I have... which is: End Date - Start date + 1)
  
  
• The Excel formula in the red box section above is: DATEDIF(Start Date, End Date, 'M') (This calculates the number of months between the start and end date, but does not take the start/ end date into account)

I apologize that this is so frustrating and confusing. I'm still super new to Alteryx, and just learning what I can and can't do in Alteryx.