Looking on the internet deeply has found these results:

in the same year is the most popular phrase on the web.

on the same year 1380,000 results on the web	in the same year 167,200,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Its rules were approved by the Pope in the same year. San Clemente was described by Karl Sapper in the same year. Helicopter flight time reached more than 4,000 hours a month in the same year. Monconys also visited Johannes Sibertus Kuffler in the same year. I joined the team in the same year as Mickey Pilone. And then, in the same year, we almost lost everything. The Polish Power Exchange opened in the same year. A Latin translation of the 'Appendix' was also published in the same year.

on the same year

1380,000 results on the web

in the same year

167,200,000 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Its rules were approved by the Pope in the same year.
San Clemente was described by Karl Sapper in the same year.
Helicopter flight time reached more than 4,000 hours a month in the same year.
Monconys also visited Johannes Sibertus Kuffler in the same year.
I joined the team in the same year as Mickey Pilone.
And then, in the same year, we almost lost everything.
The Polish Power Exchange opened in the same year.
A Latin translation of the 'Appendix' was also published in the same year.