I want to make sure we differentiate between Durations and Intervals, where Durations are times which are anchored at one end or the other by specific times, and Intervals, which describe an abstract relative time which is not anchored.
Intervals are useful:
For example: How much of this QuickTime video have I watched?
For example: When this task completes, how soon after that should it re-start
For example: What's the average time we took to display a frame
I don't see Interval in your definition list above
From the domain of human task managers it's also useful to import the concept that an interval may be in a more floppy unit than seconds. For example: "every 3 days" needs to cope with leap seconds, every Wednesday needs to cope with Time Zone changes etc.