I think Kakashi is only 28.
The Sasuke rescue arc has three flashbacks of Kakashi. One flashback says he was 12 when the Land of Waves mission happened, another states his TV introduction that he is 23-years-old and then the third flashback states he is 10 years older than Naruto which would make him 28. HIs flashbacks pick up at age 18, 11 and 7 respectively, so the statement that he’s 10 years older than Naruto may not be correct in regards to the birth date given for Naruto in either anime or manga with respect to canon timeline (I’ll stick with 23 just for simplicity). Thankfully there are some who don’t have this “10 years older” figure as clear cut!