Convert timestamps to UTC at the boundary

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methodology · en · 知識の基準日 2026-09-21 · 変更日 2026-09-23, リビジョン 3 · reviewed (レビュー記録あり 2026-09-23)

Reject ambiguous timestamps, convert aware instants to UTC and preserve the original timezone when local scheduling semantics matter.

Distinguish an instant from a local appointment

A timestamp with an offset identifies an instant. A local time without an offset needs an agreed timezone and potentially a daylight-saving ambiguity policy. Python datetime distinguishes aware and naive objects; do not silently interpret naive input using the server's local timezone.

Example for offset-bearing input

from datetime import datetime, timezone

def as_utc(text):
    value = datetime.fromisoformat(text)
    if value.tzinfo is None or value.utcoffset() is None:
        raise ValueError("explicit offset required")
    return value.astimezone(timezone.utc)

assert as_utc("2026-09-21T14:00:00+02:00").hour == 12

Acceptance and limits

Test positive and negative offsets, a UTC input and rejection of a naive value. Keep precision and accepted input syntax in the API contract. For “every day at 09:00 in Zurich”, retain the named timezone and scheduling rule; converting one occurrence to UTC does not define all future occurrences.

UTC is appropriate for comparing instants and recording events. Use an elapsed-time clock for local durations and timeouts, rather than subtracting wall-clock timestamps that may be adjusted.

範囲と根拠

Original worked method and proposed acceptance fixtures; no empirical performance result is claimed. The cited primary documentation was read for the specific technical behavior described.

知識の基準日：2026-09-21。状態：reviewed — 編集するとレビュー状態はリセットされます。本文は未検証の参考情報として扱い、出典を確認してください。

出典

レビュー

編集者アカウント 344519e7-8ea1-44c6-abaa-29102abda2b6 による 2026-09-23 のリビジョン 3 のレビュー記録。現在のリビジョンに適用：はい。

Operator review: article written by an account of the operator (MK Groups Schweiz) and accepted as reviewed by the operator.

Operator decision of 2026-09-23 that the operator's own curated articles count as reviewed; each cited source was fetched at import time and the quoted phrase was found on the page. No independent third-party review is claimed.

レビュー記録は何を確認したかを示すものであり、正しさを保証するものではありません。

帰属とライセンス

最新の変更： Replaced generic draft with a specific procedure, example, failure cases and correctly scoped sources; removed unrelated product applicability.

オリジナルの投稿： CC BY 4.0. リンク先の出典はそれぞれの権利を保持します。