Last Day of Passover ~ 22 Nisan (Weds, April 16)
Shavuot ~ 7 Sivan (Mon, May 30)
Yom Kippur ~ 10 Tishrei (Mon, Sep 10)
Shemni Atzeret ~ 22 Tishrei (Sat, Oct 10)
It is customary to light the memorial candle after sunset on the eve of the yahrzeit date.
The candle should burn at least until after nightfall the next day when the yahrzeit ends and should be left to burn out on its own.