Norwich — Norwich teachers wondering why a certain student isn’t in school on Feb. 12 or April 14 now can consult a special calendar posted on the school system website to see if there’s an important national or religious holiday on that date important to the student’s family. It’s not the official school holiday or vacation calendar, but Norwich school officials and Global City Norwich have teamed up to create a cultural calendar denoting dozens of significant events to people of different cultures and nationalities worldwide. The 2021 cultural calendar starts with Haitian Independence Day on Jan. 1 and runs through Kwanzaa Dec. 26 through Jan. 2. So far, 49 dates are listed, including 21 independence days — five Central American nations share Sept. 15 as their independence days.