Question:
If one usually holds the zman of Rabeinu Tam can one daven with a minyan maariv motzai Yom Kippur and hear havdala before Rabbeinu Tam
Answer:
It depends why the person keeps Rabbeinu Tam. If it is because you hold that this is the halacha, then it should be kept even for Yom Kippur,however if it is because for the chumra of shabbos you keep it but really you hold that it is nighttime before that, then on Yom Kippur you can be lenient because of the great need.
