What date did Alexander Fleming discover penicillin?

Alexander Fleming discovered penicillin on September 28, 1928. He noticed that a mold called Penicillium notatum had contaminated one of his bacterial cultures and was inhibiting the growth of bacteria. This serendipitous observation led to the development of penicillin, the world's first antibiotic, which has had a profound impact on medicine. Fleming's discovery marked the beginning of a new era in the treatment of bacterial infections.