How to sequentially subtract dates from one another, located in the same column?

Question

Database

How to first subtract the second from the first date, and then the third from the second, etc. so that you can display the difference in the number of months and compare? I know that there is a special function for dates, but how exactly to count sequentially? For clarity, an example table:

Answer 1

MSSQL is not at hand, but something like this:
https://docs.microsoft.com/en-us/sql/t-sql/functio...
https://docs.microsoft.com/en-us/sql /t-sql/functio...
Add column (in SELECT):
DATEDIFF(month, dates, lag(dates) over (order by dates))