find time from four bytes

Question

program in c# find time :
byte []a = new byte {224,198,23,200}; Console.WriteLine( "time {0} " ,BitConverter.ToInt32(a,0));output: -939765856
what wrong in program ,i use Convert.ToDateTime but not has correct output
i want a 32 bit integer that specifies(in seconds since midnight,january 1, 1904)