The exact date of a referendum vote depends on the specific referendum being held and the country or region organizing it.

• In Ireland, for a constitutional referendum, a bill is introduced and approved by the parliament, and then the Minister sets the polling day for the referendum vote. All eligible Irish citizens on the electoral register can vote on that date. Previous referendum dates are specific to each vote.

• In New Zealand, referendums can be held as stand-alone polls, postal votes or alongside general elections; timing depends on whether the referendum is citizen-initiated or government-initiated.

• In the UK, referendum dates are set by legislation for each specific referendum, and a timetable with key deadlines is published.

• In Australia, referendums for constitutional change require a double majority and occur on dates set by the government; past dates go back to 1901.

In summary, referendum voting dates vary widely by the particular referendum and jurisdiction, and the official polling day is generally announced formally after all preparatory steps and legal approvals. There is no fixed "when" for all referendums—each vote has its own scheduled date by official announcement.