Under Linux, sleeping time is ignored, but under Windows, it counts as execution time.
Note
The set_time_limit() function and the configuration directive max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside the execution of the script such as system calls using system(), the sleep() function, database queries, etc. is not included when determining the maximum time that the script has been running. This behavior is exhibited on *nix only. On windows set_time_limit() wins every time.