Elapsed time and clock time answer different questions
A trip lasting three hours remains three elapsed hours when it crosses a time-zone boundary. The clock at the destination can show a larger or smaller difference. Our weather timeline labels every checkpoint with that location’s time zone, rather than pretending the entire route shares the departure clock.
The custom departure field uses your device zone
The date-and-time input is interpreted in the time zone reported by your browser. A traveller planning a US drive from another country must enter the equivalent device-local time. Before submitting, the guided review also displays the resolved departure in the first checkpoint’s zone. Check both values.
Daylight-saving transitions need an extra check
Not every US location follows daylight saving time. Some local times do not exist when clocks advance, and an hour can occur twice when clocks fall back. The planner rejects a nonexistent local time. For a repeated hour, the browser resolves the occurrence: inspect the displayed UTC offset, or choose a time outside the repeated hour.
Keep the saved plan separate from the forecast
A stored departure setting is not a new forecast. A saved weather report retains its original retrieval time, and the interface withholds a current departure suggestion when you reopen that snapshot. Run a fresh check near departure, and verify official road instructions independently.
Sources and further reading
NIST: daylight-saving time rules ↗
Reviewed October 6, 2026. Product calculations are described separately from agency guidance.