public static void Main()
var dt = new DateTime(2020, 12, 31);
Console.WriteLine("Start: " + dt);
var originalDayOfMonth = dt.Day;
for (var i = 0; i < 72; i++)
var newDate = dt.AddMonths(increment);
if(originalDayOfMonth <= DateTime.DaysInMonth(newDate.Year,newDate.Month))
newDate = new DateTime(newDate.Year,newDate.Month,originalDayOfMonth);
else if(originalDayOfMonth >= DateTime.DaysInMonth(newDate.Year,newDate.Month))
newDate = new DateTime(newDate.Year,newDate.Month,DateTime.DaysInMonth(newDate.Year,newDate.Month));
Console.WriteLine($"{newDate}, DaysInMonth: {DateTime.DaysInMonth(newDate.Year, newDate.Month)}");