`start` and `end` can be in various formats, such as:
- 11:22:33
- 2024-06-01
- "2024-06-01 11:22:33" - 2024-06-01T11:22:33.456Z
What is the datetime when adding or subtracting a duration?
Duration examples include: - 5 minutes 5 seconds
- 3 weeks 4 days 5 hours
- 8 months 7 days 6 hours 5 minutes 4 seconds
- 1 year 2 months 3 days 4 hours 5 minutes 6 second 7 milliseconds 8 microseconds 9 nanoseconds