St. Nazarius and St. Celsus (1st c.) were early Christian martyrs, but nothing else is known with certainty about their lives or the time they lived, other than that they were put to death for their Christian faith in Milan, Italy, perhaps during the persecution of the Emperor Nero. For more information on Sts Nazarius and Celsus please see https://www.catholiccompany.com/morning-offering/2019-07-28/