I will share why I used to spell 'Dussehra' wrong until 2019.
Dussehra is a very popular and big Indian festival which is celebrated during October. It happens at the same as our big Bengali festival called Durga puja. But I used to spell Dussehra as 'Dussera'. Yes it can only be spelled correctly with 2 spellings 'Dussehra' and 'Dasara'. The main reason why I used to spell it wrong is because in our city Bangalore where they celebrate Durga puja in our area, near the entrance on a billboard they write it as 'Durga puja and Dussera celebration 20XX'. So I used to always feel Dussera is the correct spelling so I used to always write this spelling while chatting with my friends. But in 2019 one guy from college told me the spelling I write is wrong and he corrected. So from 2019 onward I spell it as Dussehra itself.