The names of the days of the week are mostly derived from the names of Roman gods (which current names of celestial bodies are also derived from) from the Hellenistic period, which is the period in history between the death of Alexander the Great in 323 BC and the rise of the Roman Empire in 31 BC. For instance, in the Roman calendar, Sunday is named after Sol, a Roman Sun god, and Saturday after Saturnus, the Roman god of wealth and liberation, amongst many other things. The others are a bit more obscure; Monday was named after Luna, the divine embodiment of the moon, Tuesday after Mars, Wednesday after Mercurius (Mercury), Thursday after Jove (Jupiter), and Friday after (Venus)., This weekday calculator can find the day of the week of any date. It also gives out a few fun facts as well as the calendar of the month., Weekday Calculator: What Day Is It? What day of the week was I born? Enter any date to find out the weekday and other fun facts..