On the morning of March 26, 2023, there were two correct answers to the question of what time it was in Beirut.
Lebanon's clocks had been due to spring forward overnight, but three days earlier caretaker Prime Minister Najib Mikati had postponed the change to April 20. The Maronite Patriarchate, the major TV channels and some private schools moved on schedule anyway. Government offices and public schools stayed put. Most phones jumped forward at midnight regardless, and mobile carriers sent instructions for setting them back by hand. The American University of Beirut held classes on summer time while its hospital stayed on winter time until its systems could be reconfigured.
Middle East Airlines, which followed the government, handled the split most cleanly. It shifted every Beirut departure an hour earlier on the local clock. Flight 308 to Cairo went from 06:30 to 05:30, so it left at exactly the moment it always had, and connections abroad held.
That timetable separates two kinds of appointment that usually look identical. A flight is pinned to a moment in the world; a school bell is pinned to the clock on the wall. That week the two came apart, and every calendar had to show which kind it had been storing all along.
Most computers learn each place's clock rules from the tz database, a volunteer-maintained file. Its coordinator, Paul Eggert, wrote: "Ouch, this is very short notice." He published the April date the same day, knowing many downstream software distributors take a week or more to test a change before passing it along. On March 27 the cabinet reversed Mikati's postponement and set the change for Wednesday night. Eggert's next release restored the old file, which dated Lebanon's change to March 26. He called this the best of a bad set of choices, and many devices had probably never received the April date anyway. Until Wednesday night, then, the file sided with the churches and broadcasters against the government. It can hold only one answer for Beirut, with no way to record that the answer depended on whom you asked.
RFC 3339, the 2002 standard behind most internet timestamps, had stepped around this kind of instability long before. It recommends recording times in UTC, the reference clock that never shifts for daylight saving, precisely because legislatures change local rules unpredictably. For logs, payments and departures that was the right design, and the same choice the airline's schedulers made by hand.
Store Mass at ten or school at eight the same way, though, and when a government rewrites the rules on a Thursday, the entry ends up an hour away from when people actually show up.
RFC 9557, published in April 2024, lets a timestamp also carry its time zone's name, such as Asia/Beirut, so software can detect when a stored instant no longer matches the rules. It goes no further: the standard says it "does not address" future local-time events that politics moves, leaving that decision to someone outside the format.
I think its authors drew that line in the right place. No format can know whether a patient's appointment followed the hospital's clock or the ministry's. That judgment used to belong to whoever made the promise, because they knew which clock they meant. Increasingly it belongs to an assistant that books the nine o'clock slot, saves an instant and moves on, having answered the Beirut question without asking it. A wrong guess costs whoever stands at a locked door an hour early, not the software that made it. In 2023 people could at least argue it out at the door. The calendar entry still has no field for the fact that would settle it, which is whose clock the promise was made on.
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A year's notice, please: The tz project's coordination guidance for governments asks officials to send the actual legal text and announce clock changes at least a year ahead, because releases still have to pass through distributors before reaching devices.
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What software should do: Section 3.4 of RFC 9557 lets a timestamp mark its named zone as critical, which forces software to act on a mismatch by rejecting the value or resolving it with user input or programmed behavior.
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The missed appointments themselves: L'Orient Today's chronicle of the aftermath records what the split cost ordinary people once the country had officially changed its clocks.
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Workarounds from the maintainer: In the original mailing-list thread, Paul Eggert suggested stopgaps such as a hand-written POSIX time-zone string for systems that could not wait for an update to propagate.
