Introduction | When Time Isn't Continuous | Empty Intersections | Punching Holes in Intervals | Unions of Non-Overlapping Spans | Subtracting an Interval from Itself | Case Study: Employment History | Merging Intervals | Finding Gaps | Edge Cases and Gotchas | Abutting Intervals and Intersection | Instantaneous Intervals and Set Difference | Time Zones | Comparison with Datetime Vectors