When Shakespeare wrote Troilus Cressida and the sources he used for the play.
The exact date of composition for Troilus and Cressida is not known. Although there is mention of the play in the Stationer's Register in 1603, its first publication was in Quarto form in 1609. Critical opinion has generally agreed that stylistically it is likely the play was written between 1600 and 1603, at a similar time to when Shakespeare wrote Hamlet and Measure for Measure.
The story of the Trojan War had been one of the most popular elements of 'history' in England from the Middle Ages on, and in Shakespeare's day, Homer's Iliad was available in several translations. This supplied the epic background, but not the love story of Troilus and Cressida, for which Shakespeare was likely indebted to Chaucer's poem Troylus and Criseyde and Robert Henryson's Testament of Cresseid. Other details of the play can be dated back to works from the fifteenth century.