Nowadays we don’t know for sure the dates and original versions of Shakespeare’s plays, because there was no documentation of his plays and works, except for Venus and Adonis and Lucrece. They were  in fact mythological poems. and the theatre was not considered literature. To tell the truth, men of theatre were people concerned only with the staging of the plays they wrote, taking sometimes part to them with acting or directing.

On the contrary, the most successful plays were often published even if without the playwright s permission because they were taken from copy-books or prompt-books, sometimes also from memory of players themselves. As a result they were often unreliable.

The unreliable editions were called bad quartos, called in this way because of their size where the whole sheet of paper was folded twice to form four leaves.

The first accurate and complete edition of Shakespeare’s works was published in 1623 by Hemminges and Condell. Texts we read today are not the original because they’re reconstructed by philologists.

A further problem is to give works a date and we have to take into account external and internal evidence in order to do that. The first one is referred to citations mentioned in books or in the Stationer’s Register or from contemporary documents. The second one consist in looking for references to contemporary historical events or also to expressions and images that came from other books.

Something that could also help us is the consideration of the style of plays: Shakespeare has used different ways of writing as he made use both of prose and verse. 

One of the most important attempts to date Shakespeare plays was made by E. K. Chambers.