calculating future dates involving half months and minus amounts of days

[defaultn8sphkiqnsa1]

I have a form that calculates many future dates; I did not create it but now have been given the task of correcting the calculations. An example: Filing date 02/19/2021 task needing to be done next is in 13 months which we have as 03/19/2021. The dates should always be the same date in the month but when using the number of days it's slightly off. I know I can change it to months not days but there are times we have 31.5 months or 29 months -10 days and I have not been able to make that work. Does anyone know of a way to either have both months and days in the calculation or perhaps just a way to do this in general? I've only just recently started using Adobe as I am now and I'm still very new so any help is greatly appreciated! 

[John T Smith]

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