Courtesy of Ben Myers.
In 1948 the World Council of Churches proposed to establish a Commission on Late Arrivals. However, plans were abandoned when it became apparent that the representative churches were unable to agree on a definition of the word “late”. A prominent Greek Orthodox delegate argued that “lateness” designates arrival more than twenty minutes after the specified starting time; while several Presbyterian theologians insisted that “lateness” technically refers to any arrival less than three minutes prior to starting time. These thorny and intractable questions of definition perhaps belong more to the philosophy of time than to liturgical studies, and as a result I make no attempt to resolve them here. The following ecumenical manual has been prepared simply as a general guide to the differing Liturgical Rules for late arrivals in various church traditions. It is hoped that this manual will lay the foundation for further study in this field, and that it will prove useful as a practical aid for those emergencies of punctuality that can strike even the most conscientious of churchgoers.
(I’m mostly sure that paragraph was a joke.)