good afternoon

hope you are fine

as per your query to be eligible in UPSC Exam your age must be 21 years old as on 1st August of the year  with your date of birth in 8 April 2005 , you will be 21 years old on after 1st August 2026 . So, You will become eligible in 2027  (UPSC 2027)

Maximum age limit is 32 years, also there's 3  year relaxation on upper age limit for OBC and of 5 years for SC/ST category.

for more information about UPSC Checkout given link below:
https://competition.careers360.com/articles/upsc-ias-eligibility-criteria/amp

Hope you found it helpful
All the best!!!