Sonnet 104 states three Aprils have passed since Shakespeare first met the fair youth. Some scholars think that Shakespeare is speaking metaphorically but I disagree. I suspect that April of 1592 had special significance for Shakespeare.
Three Aprils and three hot Junes passed means that sonnet 104 was written in the summer of 1594 and implies that Shakespeare first met Wriothesley in April 1592.
This could definitely be correct. Between Feburary and June 1592 Lord Strange's men performed a repertory of 23 plays that included one or more of Shakespeare's Henry V1 trilogy. This play must have been performed prior to June 23rd 1592 because this was when the theatres were closed due to an outbreak of the plague.
The Shakesperian play could easily have been showing in April of 1592 because records show that it was definitely performed on the 3rd of May 1592.
Wriothesley was an avid playgoer he may have seen this play in April 1592 ,enjoyed it and afterwards made Shakespeare's personal acquaintance.
Perhapst this was the beginning of their friendship.
I date the events of the love triangle to mid to late 1594 and believe that most of the sonnets were written between 1593 and 1594. Willobie His Avisa confirms this timeline.
Another factor to consider is that the craze of sonnet writing was at its height in 1594 but had become far less popular by 1597.