Here is a typical PhD timeline, provided by SEAS: http://www.seas.harvard.edu/academics/graduate/phd-timeline
The PhD Degree Requirements can be found here: http://www.seas.harvard.edu/academics/graduate/graduate-degree-requirements
Deadlines for Degree Applications are listed here: http://registrar.fas.harvard.edu/registration-enrollment-degrees/graduation-diplomas
A Note on Writing Your Dissertation
We sincerely hope that you do not attempt to write your thesis in Word. Please learn LaTeX. It is a crucial tool for writing scientific papers. Many publishers have LaTeX templates that automatically format the page layout, fonts, headings, etc. for you. Bibliographies, references, figures, equations become much simpler to deal with. There is an unofficial thesis template for Harvard, which can be accessed here: https://www.sharelatex.com/templates/thesis/harvard-phd
