time.h直接替换：time_t表示ANSI-C或C99中的值（年<1970）和（年> 2038）

I have a piece of code in ANSI C which uses the time.h library and time_h structures to (amongst other date-related calculations) work out the interval between two given dates. This works fine but this limits my code to input between 1970 and 2038. I would now like to make my code more general.I have a piece of code in ANSI C which uses the