You know, once upon a time I really did have this all written out somewhere....I think it was posted over on e.a.r....
Anyhow.
Seerow's Kindness results in a Yeerk uprise in 1966
Hork-Bajir invasion begins 1968, ends 1969/1970
Sometime between 1970 and 1975 the Yeerks make a deal with the Taxxons and set up a base on their world.
The Andalite Chronicles begins 21 years before The Invasion. That would be 1975. This is they year that the Yeerks discovered humans and that Edriss went to Earth and began to establish stuff there. During the time from approximately 1975 to 1994 Edriss is in charge of Earth. Sometime in 1994/1995 control over the operation shifted to Visser Three and Edriss left Earth, resulting in Eva's "death". 1996 is when the Animorphs begin to fight.
As for the timeline of the main series, it's a bit more convoluted.
Generally, books 1-3 occur during about a months time. Book 15 or 16 marks the one year point.
The issues with David come shortly after the one year point, and I'm guessing the two year point hits around book 30, leaving books 31-54 to take place during the remaining time.
The final story arc probably occurs over maybe a month, tops, I think.