(IsraelNN.com) The fast of Tisha B'Av, the "saddest" day in the Jewish calendar, begins on Saturday night as the Sabbath ends, and ends Sunday evening at sundown.  Its name literally means "the ninth day of the Jewish month of Av," the date of some of the gravest tragedies to have befallen the Jewish People.  Most notably, both Holy Temples in Jerusalem were destroyed on Tisha B'Av, but the list of calamities includes also the following:

• G-d decreed, following the Sin of the Spies as recounted in Numbers 13-14, that the Children of Israel would not be allowed to enter the Land of Israel until the entire generation had died out.
• The fall of Beitar, the last fortress to hold out during the Bar Kochba revolt in the year 135 C.E., fell to the Romans, marking the last milestone in the beginning of our current Exile.
• A year later, the Temple area was plowed under.
• The Jews of Spain were expelled by King Ferdinand and Queen Isabella in 1492. 
• World War I erupted in 1914.
• The Jews of Gush Katif spent their last legal day in their homes in 2005, and were expelled three days later.

"Secular Jews for the Temple"
The centerpiece of Tisha B'Av mourning is the destruction of the Holy Temple (Beit HaMikdash).  Among the many groups that have sprouted over the past several years promoting awareness of the Beit HaMikdash is one named "Secular Jews for the Temple."  Ahuvyah Tabenkin of left-wing Kibbutz Ein Harod said, "It's true that we don't exactly represent a majority of secular Kibbutz members... but the pioneers have always been a minority: the Zionists were a minority among the Jews, those who came to the Land were a minority among the Zionists, those who worked the land were also a minority, and now we are a minority as well.  But I hope that soon we will be the leaders."

Tabenkin has nationalist, political and historical reasons why the Temple and the Temple Mount are important.  Asked if he has religious considerations as well, Tabenkin told Arutz-7's Ariel Kahane, "Well, the word 'religious' can be the subject of long discussions.  Look, the Gerrer Rebbe once said, 'When the Haskalah [Enlightenment] came to the world, with science, physics, etc., we [the religious] left it for the secular Jews; when Zionism came to the world, we gave that too to the secular; and now we have also left the Repentance Movement for the secular.'  Accordingly, it looks like we [the secular] will also have to build the Beit HaMikdash."

Asked whether he calls for the actual construction of the Temple, he said, "There are many religious authorities, including Maimonides, who say that the Temple must be rebuilt, and so I think it should be done...  As a first step, we must show that we control the Temple Mount... I call upon all of Israel to come to the Mount on [Tisha B'Av] and show that it belongs to the Jewish nation."  

Prominent rabbis permit the ascent to parts of the Temple Mount after certain Halakhic precautions have been taken.

Tisha B'Av Laws
The Sages enacted Yom Kippur-like restrictions on Tisha B'Av, including no eating, drinking, washing, or marital relations. Leather shoes are not worn, and even Torah study - a major source of Jewish joy - is restricted to topics connected with the Destruction of the Temples, Tisha B'Av, and the like.  

Though the afternoon before Tisha B'Av is generally marked by mourning-like practices, this is not true this year, when the eve of Tisha B'av is on the Sabbath. The afternoon Third Meal is larger than usual, as it will be the last meal for over 24 hours, and the usual Sabbath songs are sung.  However, one must not eat after sundown on Sabbath, even though the Sabbath has not yet ended.  

When three stars have appeared, the "short Havdalah" is recited ["Blessed is He Who separates between Sabbath and weekdays"], and Tisha B'Av officially begins; leather shoes are removed and unlaundered weekday clothes are worn.  The evening prayer service is followed by one of the Havdalah blessings, that of "light," and Eichah (Book of Lamentations) is read aloud. 

The other Havdalah blessings are recited on Sunday evening before eating; the blessing on spices is not recited at all this week.  Those who feel they must eat on Tisha B'Av for health reasons should consult an Orthodox rabbi.