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Date-line weekday divergence
Across the International Date Line the same UTC instant is a different local weekday. Kiribati (+13/+14) and Samoa (+13) are a full day ahead of the Americas, so an event's local weekday can differ from the weekday of its UTC slot — the temporal analog of the geo antimeridian.
Class
Case to account for
Affects
3 conversions
01
Detection
|zone offset| approaches or exceeds 12 hours.
02
Mitigation
01
Keep the canonical slot on UTC; annotate the local weekday separately; expect local-week ≠ UTC-week near the line.
03
Affected conversions
Timestamp + zonehour-of-week slot
OPENInstant(ISO week × slot) key
OPENsemantics
OPENMore in Date line
Extreme offset span (UTC−12 … +14)