One Day tells the story of Emma Morley and Dexter Mayhew who, on 15th July 1988, the night of their graduation, speak for the very first time. The next morning, they go their separate ways but where will they be on this one ordinary day the next year, and the year after that, and every year that follows? Each episode finds Dex and Em, one year older, on this one particular date, as they grow and change, move together and apart, experience joy and heartbreak. One Day is a decades-spanning love story, based on the worldwide bestseller by David Nicholls.