The hour that disappears—or happens twice
A practical explanation of skipped and repeated local times.
The forward jump creates a gap
When a region moves its clock forward, a range of local times may not occur that day. A requested time inside the gap cannot identify a real instant without an additional convention.
The converter rejects that input by default. You can then change the time or explicitly choose the earlier or later interpretation across the gap.
The backward jump creates an overlap
When the clock moves backward, some local times happen twice. A time such as 01:30 can refer to two different instants with different UTC offsets.
Choosing “earlier” selects the first occurrence. Choosing “later” selects the second. Include the offset when sharing a schedule near a clock change.
Use local dates and named zones
Do not assume a recurring meeting has the same UTC time all year. Decide whether the meeting should follow the organizer’s local clock or a fixed global instant, then communicate that choice.