Answer by Adam Janovec for Difference in months between two dates

one line solution

For first, check if both dates are in current year, if not get months of whole years and then add months from start and end year.

DateTime dateFrom = new DateTime(2019, 2, 1);DateTime dateTo = new DateTime(2021, 5, 25);

With first month

var monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (13 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month + 1;

result = 28

Without first month

monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (12 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month;

result = 27