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Shabbat begins when the sun goes down on Friday, and ends on Saturday when the sky gets dark enough for three stars to be visible. There is a mitzva to extend the sanctity of Shabbat by beginning it early (before sundown) and ending it late (after the stars have come out). This extra time is referred to as tosefet Shabbat (addition to Shabbat). It demonstrates that Shabbat is so beloved that we are keen to welcome it in and reluctant to let it go. Furthermore, by transforming a few weekday minutes into Shabbat, we link the mundane and the sacred, elevating the six workdays. When Jewish calendars list Shabbat times, they take tosefet Shabbat into account. Typically, the time given for the start of Shabbat is eighteen minutes before sunset in the diaspora, twenty minutes in Israel, and forty minutes in Jerusalem. The time listed for the end of Shabbat is ten to fifteen minutes after the stars become visible.
Customarily, women accept Shabbat upon themselves when they light the candles, preferably at the time listed in the calendar. After they light, they may no longer do melakha. Men customarily accept Shabbat upon themselves in synagogue during the prayer service of Kabbalat Shabbat (Accepting Shabbat) before Ma’ariv. They should make sure to have this acceptance in mind a few minutes before sunset.
