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国際会議タイムプランナー

複数都市のメンバーが無理なく参加できる最適な会議時間帯を見つけます。

Plan the meeting

仕組みと計算ルール

  1. You schedule in the reference zone: its local date and start time are resolved to one exact instant (daylight saving on that date included).
  2. The meeting’s end is computed as start + duration in absolute time. Every row then shows the same two instants as local wall times in that participant’s zone, with its own offset resolved per endpoint.
  3. The "Day" columns flag previous day / next day relative to the reference date, which prevents missed calls, and a note appears when clocks change mid-meeting.

知っておくと便利なポイント

  • The reference zone is always the first row; a participant equal to the reference is skipped as a duplicate.
  • If the start time does not exist (spring-forward gap) or occurs twice (fall-back overlap) in the reference zone, the planner says so and states which instant it used.
  • Up to 12 participant zones.
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タイムゾーン変換（時差計算）

世界中の任意の2つのタイムゾーン間で日時を正確に換算します。

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2都市間の時差計算

2つの地域やタイムゾーンの間の正確な時間差を計算します。

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世界時計

世界の主要都市の現在時刻をひと目で並べて確認できます。

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サマータイムチェッカー

各タイムゾーンにおける夏時間の実施状況や切り替え日時を確認します。

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よくある質問

How does the planner pick the reference time?
The first zone in your list is the reference; its local date and time are what you schedule. Every other row shows the same absolute instant in local time.
Why do some rows show a different date?
Because the meeting lands on another calendar day there. The planner marks Previous day / Next day explicitly, which is exactly the detail that prevents missed calls.
What if the meeting spans a DST change?
Duration is measured in absolute time, so if clocks change mid-meeting the start and end offsets may differ. Each row shows the offset in effect for its endpoint.