How to count the number of days until the nearest 25th day (of a month) in C#.NET?

Question

.NET

It is necessary to count the number of days until the nearest 25th.
That is, if today is the 20th (of any month), then the program will display the number 5.
If today is the 28th and this month has 30 days, then the program will display the number 27 (2 days before the 30th + 25 days).

Answer 1

static int DaysTill25(DateTime dt)
{
   return dt.Day <= 25 ? 
                       25 - dt.Day
                     : 25 + (DateTime.DaysInMonth(dt.Year, dt.Month) - dt.Day);
}