Sunset today marks the beginning of Yom Kippur, the holiest and most solemn observance of the Jewish year.

From sundown tonight until the sounding of the shofar (ram's horn) 24 hours later, observant Jews will spend their time in reflection and prayer, imploring forgiveness for their sins of the year past before the gates of Heaven close for the year at sundown tomorrow.

Yom Kippur falls 10 days after Rosh Hashanah, the beginning of the Jewish New Year, when the Book of Life is opened and believers are admonished to examine their lives for the year and make amends. The period between Rosh Hashanah and Yom Kippur is known as the Days of Awe.

Pious Jews fast during Yom Kippur.

One of the highlights of synagogue services tonight is the chanting of the Kol Nidre, a declaration that absolves believers from vows they have made during the year that were impossible to fulfill. The Kol Nidre, literally, "all the vows," assumed particular importance during the Inquisition in Spain and Portugal when many Jews were forced to convert to Christianity on pain of death.

Under those circumstances, Jews who continued secretly to hold to their Jewish faith were released from their forced conversions by the Kol Nidre.

Jewish children are excused from public schools tomorrow and adults are not expected at their workplaces.