Well a timer service is a different type of service. Not sure I can find you a good reference, but read for example the beginning of this article:
"The other subsystem is just called "kernel timers"; it offers less precision but is more efficient in situations where the timer will probably be canceled before it fires."
Something like a Timer#reset() method, which resets the countdown to the event, is not natural with a task scheduler, although you can surely emulate it sort of.
They are related, but different.
You can read about Linux timerfd_settimer or POSIX setitimer to get a better feeling for what a timer service might offer.