I thought I knew the Correct way, but I realized. I misunderstood , What I heard About calculating the time. I thought it was Sunrise and sunset time , divided into 2. And also misunderstood the 5th hour ending time, I read that we should pray before the 5th Hour, so I thought Isha always ends 5 hours After The Isha time.
Oct 10th, 2015
There is nothing to do, as you have done this out of ignorance. You have to pray at the correct time henceforth.