Hello Aspirant,Hope you are doing well

You are eligible to write JEE mains till 3 years after completion of your class 12. If you have passed your class 12th in 2021, you are eligible to write JEE mains in 2021, 2022 and 2023.

You can write JEE Advanced only till 2 years after completion of your class 12th. That is in 2021 and 2022.

For further details visit this

https://engineering.careers360.com/exams/jee-main

Hope this helps
All the best