This year, 2010/ 5770, The Nine Days (the Hebrew month of Av 1–9) occurs July 12–July 20. Tisha B'Av is July 20.
Next year, 2011/ 5771, The Nine Days (the Hebrew month of Av 1–9) occurs Aug. 1–9. Tisha B'Av is Aug. 9.
For more info on the actual fast day, itself go to Chabad.org here: Calendarchabad.org:
More information on the observance of The Three Weeks (the time period that brackets The Nine Days), try here: Calendarhere.
