Question:
If a person was niftar during Adar of a regular year, when does one observe the yohrzeit during leap year (Adar I or Adar II) ?
Answer:
There are various customs regarding this. The Sefardi custom is to observe the yahrtzeit during the second Adar. The Ashkenazi custom however is to observe he first Adar and if possible the second one also.
Best wishes
Sources:
O:CH 568-7.