As of June 2025, open almost all day weekends & weekday evenings - see attached screenshot. You first go to the tourist information center to fill out a short registration form (that's where the screenshot is from) and then go to the other entrance where you'll make payment and climb the tower. Gorgeous views.

(Only open Saturday and Sunday in October 2024. 50 UAH entry fee. You have to pick up a permit at the Tourist Info Office first, in the same building). A long climb of about 300 steps to the top of the tower, but definitely worth it for the excellent views of the city centre. You will also be half-deafened by the bells ring every 15 minutes!