Method Deck / timezones

Flight duration across time zones

Computes elapsed travel time from a departure local date/time/offset to an arrival local date/time/offset.

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Inputs

• departure_date (string, required) : ISO 8601 departure date, YYYY-MM-DD, local to departure_offset
• departure_time (string, required) : Departure local wall-clock time, HH:MM or HH:MM:SS
• departure_offset (string, required) : Fixed UTC offset at departure, e.g. -05:00
• arrival_date (string, required) : ISO 8601 arrival date, YYYY-MM-DD, local to arrival_offset
• arrival_time (string, required) : Arrival local wall-clock time, HH:MM or HH:MM:SS
• arrival_offset (string, required) : Fixed UTC offset at arrival, e.g. +01:00

Outputs

• hours: Whole hours of elapsed time
• minutes: Remaining minutes of elapsed time

Steps

1. Parse the departure date, time and offset into a single UTC instant, in seconds: day-number (Hinnant days_from_civil, cited above) times 86400, plus local seconds-since-midnight, minus the offset in seconds.
2. Do the same for the arrival date, time and offset to get the arrival UTC instant.
3. elapsed_seconds = arrival_utc_instant - departure_utc_instant; require this to be positive.
4. hours = floor(elapsed_seconds / 3600); minutes = floor((elapsed_seconds mod 3600) / 60).

Constants

None.

Sources

• chrono-Compatible Low-Level Date Algorithms (Howard Hinnant, 2026-09-30T19:41:35Z) - day-number kernel used to place both wall-clock times on a single UTC instant line; no time zone database is used

Worked example and test vectors

Published card

• Address: 1a135c4eaff94ccb876a7f71fc5a357d
• Made at: 2026-09-30T22:39:30.722Z
• Method sha256: bac6ae55771be31f50c744cb731431c2f7319b904ab49f1dbf900d6d29fa14b2