To get the numbers with 0 padded on left, you will have to use string format.
int doy = DateTime.Now.DayOfYear;// Day of the year
string yr = DateTime.Now.ToString("yy");// Two digit year
string mon = DateTime.Now.Month.ToString("d2"); // Two digit month (zero on left for small numbers)
string day = DateTime.Now.Day.ToString("d2"); // Two digit day (zero on left for small numbers)
Console.WriteLine(doy);
Console.WriteLine(yr);
Console.WriteLine(mon);
Console.WriteLine(day);
solved How can I find the day of the year, year, month and day for now in C#? [duplicate]