You can use RClock as an advanced timer, or as it is ment: as a relative clock. A relative clock starts counting when you open it and lets you interrupt it or pre-program interruptions or add them later. A relative clock serves as a working tool to let you plan a project or other task in relative hours.
For example:
16h00 - 17h00: Clean laundry
17h00 - 19h30: Go Shopping
21h30 - 21h45: Rest
21h45 - 22h00: Prepare for excursion
22h00 - ????: Excursion for unknown duration.
This might seem convenient, but when you don't know beforehand when you will start your schedule, you have to say "the first hour this, the second hour that...", so your hours will be relative to the starting hour.
0h00 - 1h00: Clean laundry
1h00 - 2h30: Go Shopping
2h30 - 2h45: Rest
2h45 - 3h00: Prepare for excursion
3h00 - ????: Excursion for unknown duration.
Where you know that if you start at 16h30 it means: 16h30 - 17h30 and so on. Now if an unplanned interruption comes along from 17h30 till 19h30, your schedule is knocked out thus you need to rearrange it. But instead you can simply use a relative clock which calculates these working hours for you, relatively. Thus actually it simply counts "first working hour, second working hour..." which is very useful for a lot of tasks that have no actual deadlines, are not appointments or simply have no predefined absolute hour.