Holy days for Judaism

People who are not Jewish will variously tell you the Jewish holy day, the Shabbat, is Friday or Saturday. They're both correct to an extent, because the Jewish day begins at nightfall rather than at midnight as is the case with the secular calendar. As a result, Shabbat starts at nightfall on Friday (though Shabbat prayers are said and candles lit shortly before nightfall) and ends shortly after nightfall (havdalah) on Saturday.