Sent: Monday, August 31, 2009 10:08:06 AM
Subject: RE: Kaddish
Basically, your mourning ends at the date of burial minus one day (ie: a complete year) which ends at nightfall after mincha the date before the burial date. So the burial was Teves 20, so your mourning period ends at nightfall of Teves 19.
Kaddish ends a month before at mincha on Kislev 19.
Yahrtzeit is the day of his passing which is Teves 18 (from maariv the night before until nightfall the day of).