SELECT      t.date_,
            t.user_id,
            t.cnt,
            o.count AS without_activities
FROM        [table] t
OUTER APPLY
            (
                   SELECT COUNT(*) AS count
                   FROM   [table] tt
                   WHERE  tt.date_ < t.date_
                   AND    tt.user_id = t.user_id
                   AND    tt.cnt = 0
                   AND    tt.date_ >
                          ISNULL((
                                 SELECT MAX(ttt.date_)
                                 FROM   [table] ttt
                                 WHERE  ttt.date_<t.date_
                                 AND    ttt.user_id = tt.user_id
                                 AND    ttt.cnt !=0),-1) ) o;