Having previously recorded that the LHC re-started on Crystal Day, April 5, 2012 after the winter shut-down, I now find that it also restarted on the same date in 2015 after having been shut down for 2 years for the major upgrade. So it looks like the machine itself is celebrating the date! The CERN Courier describes the event as follows:

Proton beams are back in the LHC

After two years of intense maintenance and consolidation, and several months of preparation for the restart, the LHC is back in operation. At 10.41 a.m. on 5 April, for the first time in more than two years, proton Beam 1 completed an anti-clockwise circuit of the 27-km ring at the injection energy of 450 GeV. Injected at point 8 on the LHC, Beam 1 was allowed round the ring one step at a time, as collimators were opened at each point in turn, once the operators had checked that all was working well. On the way, the protons provided the first “beam-splash” events for the ATLAS and CMS experiments, at points 1 and 5, respectively (see “Inside (photo)story”). Beam 2 then followed a similar procedure. Injected at point 2, it completed its first orbit in the clockwise direction at 12.27 p.m.