What This Site Is
LHC Timer is an independent countdown to the restart of the Large Hadron Collider as the High Luminosity LHC. The machine stopped colliding on 27 June 2026 and will spend about four years being rebuilt. We think that is one of the great scheduled moments in science, and it deserved a proper clock.
Around the countdown we maintain a small library of plain language guides covering the shutdown, the upgrade, the machine's full timeline and the safety questions people still ask.
Where the Date Comes From
The target comes from CERN's published accelerator schedule, which currently puts first HL-LHC beams in June 2030. CERN has announced the month but not an exact day, so the timer counts to 15 June 2030 as a midpoint placeholder. The day CERN announces a precise date, the countdown switches to it. When the schedule moves, so do we, and we say so rather than quietly editing.
What This Site Is Not
It is not affiliated with, endorsed by, or operated by CERN, and nothing here is an official communication. For official news, schedules and press material, go to home.cern. If our copy and CERN's ever disagree, CERN is right and we owe an update.
Accuracy
Every fact on this site is anchored to CERN announcements, published schedules and the experiments' own material. Guides state the schedule as a target, because that is what it is. Accelerator physics is done by people, and dates built from thousands of dependent tasks can move in either direction.