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Box of dates

Each year Joe buys a simple calendar that just shows year, month, day and date. This year he realised that if he starts saving each year’s calendar he will eventually have a full set of different calendars and will never need to buy one again.

For which year will Joe buy his last calendar?

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 28 July. The Editor’s decision is final. Please send entries to Enigma 1601, New Å®ÉúСÊÓƵ, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).

Answer to 1595 All mapped out: 636 millimetres

The winner Jim Jamieson of Marlow, Buckinghamshire, UK