Formula for calculating number of months between two given dates

[hubyh]

I am trying to build a formula to establish the number of months between the start date of a project and the end date of the project.

With Start date of 2022-09-01 and end date 2023-08-31 that is 12 months, the formula I was using below, which I thought was correct, is calculating 11 months. Where am I going wrong with this?

DateTimeDiff([ProjectEndDate],[ProjectStartDate],"months")

[DataNath · Accepted solution]

Hey @hubyh, 11 is correct here, no? At 2023-08-31 only 11 full months have passed, 12 months would need the end date to be a day later i.e. 2023-09-01:

[Zok]

11 full months

(12-9)+8=11

With your logic, your birthday would be one day earlier each year

You should calculate the difference in days and divide it by 30 to be more precise

[hubyh]

Thank you DataNath

I am new to this, so this is going to cause a problem with my data.  Can I use this formula but get it to add 1 day to the end date ?  If so what would that formula be?

[Zok]