sixth anniversary of a death
Refers specifically to the Buddhist memorial service held on the sixth anniversary of a person's death, counting the year of death as the first year.
Next month is the sixth anniversary of my grandmother's death.
Compound of 七 (seven) + 回忌 (anniversary of death). The term uses the traditional Japanese age-counting system where the year of death is counted as the first year, making the sixth anniversary the 'seventh' memorial service.