In most of the industrialised world, the first day of May is celebrated as a day to honour those who labour, and is frequently cause for rallies and demonstrations as well as picnics and parties. Unions are at their most militant and calls for unity and solidarity among the fraternity of labour are at their most vocal. There is a reason why this particular holiday falls on that particular day. May Day, as International Workers' Day, actually commemorates an event that happened in the United States, one of the few industrialised countries in which it is not recognised as a holiday.