How to implement Task Scheduler Manager on C# ? : I want to write a Scheduler Manager.  
My Scheduler Manager contain 3 type of running task  
 
     - each XX seconds ( ex. each 15 seconds )  
     - every day at same time ( ex. every day at 7 a.m )  
     - emergency task - this is task that UI can add and will run imitatively


My problem is that i don't know how to implement the alarm that will popup at the time that the task need to run. 

I can calculate the time between 'now' and the target time and using Timer.Interval that will wait for the right time to popup the task 
 
But is there better way to implement this ? 