int year;
if((year%4==0&&year%100!=0)||(year%400!=0))
Console.WriteLine("2月份为29天");
else
Console.WriteLine("2月份为28天");
int year;
if((year%4==0&&year%100!=0)||(year%400!=0))
Console.WriteLine("2月份为29天");
else
Console.WriteLine("2月份为28天");