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ISO 8601変換

日時を国際標準ISO 8601形式の文字列に変換・解析します。

Parse an ISO 8601 string

Accepted: date-only · T separator · optional seconds and fraction · Z or ±HH:MM offsets.

Build an ISO string

仕組みと計算ルール

  1. ISO 8601 writes one moment as YYYY-MM-DDTHH:MM:SS plus an optional fraction and offset; Z means UTC, and +05:30 means local time 5 h 30 m ahead of UTC.
  2. Parsing: strings with an offset identify one exact instant; the tool normalizes them to UTC, shows the Unix timestamps, and renders the instant in UTC and your local zone.
  3. Building: your date, time and zone are resolved to an instant (daylight saving included), then emitted with that zone’s offset, plus the UTC (Z) form and Unix seconds for cross-checking.

知っておくと便利なポイント

  • Offset-less strings (2026-10-28T14:30:00) are shown as written with both the UTC and your-zone interpretations, never silently assumed to be one or the other.
  • Date-only strings (2026-10-28) are reported as dates; the implied midnight zone differs across systems, which the tool states rather than guessing.
  • RFC 3339 is the internet profile of ISO 8601 that APIs actually use; strings like 2026-10-28T14:30:00Z satisfy both standards.
タイムスタンプツールおすすめ

Unixタイムスタンプ相互変換

タイムスタンプを日時に、日時を秒・ミリ秒のタイムスタンプに変換します。

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Unixタイムスタンプから日時に変換

数値をUTCおよびお使いの端末の現地時刻の日付・時刻に変換します。

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タイムスタンプツール

日時からUnixタイムスタンプへ変換

任意の日付と時刻をエポック秒およびミリ秒に変換します。

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UTCタイムスタンプ変換

タイムスタンプを時差なしの純粋なUTC日時に直結して変換します。

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よくある質問

What does the “Z” in an ISO string mean?
Zulu, meaning the string refers to UTC. 2026-10-28T14:30:00Z is 14:30 UTC. A string with +02:00 instead describes local time two hours ahead of UTC; both denote a precise instant.
What if my ISO string has no offset at all?
Then it is ambiguous: 14:30 somewhere, but where? The tool shows it as written and explains that an offset (or Z) is required to pin down an instant, rather than silently assuming one.
Is ISO 8601 the same as RFC 3339?
RFC 3339 is an internet profile of ISO 8601, representing a subset with a fixed layout. Strings like 2026-10-28T14:30:00Z satisfy both specifications.