From GameWatcher: “Normally an event is held on schedule, and the Fallout 76 Fasnacht Parade Event was expected to be live between May 25th and June 2nd. Unfortunately, an issue discovered after the event start time has caused Bethesda to roll back the changes, meaning Fasnacht Parade is currently delayed.”
Source: N4G PC Fallout 76 Fasnacht Parade Event – When Does It Begin and End?