For the past 15 years, Kossar’s Bialys has been closed on Shabbos, reopening after the sun goes down Saturday evening. But earlier this month, that all changed.

The Lower East Side institution, located at 367 Grand St., is now open Saturdays from 6 a.m.-midnight. This past summer, Marc Halprin and Evan Giniger bought Kossars and have been making small tweaks in the business in the last few months). The decision to close for the Jewish sabbath was made by previous owners Juda Engelmayer and Danny Cohen, observant Jews. Tomorrow, Christmas Eve, Kossar’s will be open until 4 p.m. On Christmas Day, the hours will be 9 a.m-5 p.m.
Yes, see here: https://lo-down.mystagingwebsite.com/2013/12/kossars-will-reamin-kosher-even-with-saturday-hours.html