The messy history behind the modern calendar

This year, the UK has had its hottest May and June days on record, with the mercury hitting the high thirties.But while the markings on a thermometer seem scientific and regular, the way we split up our calendar does not. Why, for instance, does May have 31 days and June have 30?To find out why our calendar has its modern form, we speak to Kristen Lippincott, former director of the Royal Observatory at Greenwich, and author of The Story of Time. If you have seen a number in the news you think we should take a look at, email moreorless@bbc.co.uk Presenter: Tim Harford Producer: Josh McMinn Series Producer: Tom Colls Programme Coordinator: Brenda Brown Sound Engineer: Giles Aspen Editor: Richard Vadon