time.h can't add

while compiling time serial program from example programs the following error message is occuring "Build options changed, rebuilding all
TimeSerial.ino:13:20: fatal error: Time.h: No such file or directory
compilation terminated.
Error compiling."

how can i add time.h

What did you change ?

nothing i have changed

Well, something changed.
Did you stop and restart the IDE after you initially installed the library ?

Why did you start 2 threads about this problem ?