Yom Hazikaron is the Israeli Memorial Day.
Yom Hazikaron is observed on the 4th day of the month of Iyar of the Hebrew calendar, always preceding the next day's celebrations of Israel Independence Day, Yom Ha-Atzma'ut, on the 5th day of Iyar, the anniversary of the Proclamation of the State of Israel in 1948. Both days may be moved one day or two earlier (the 3rd and 4th, or the 2nd and 3rd, of Iyar) if either the 4th or the 5th happens to occur on a Saturday, the Jewish Sabbath. Similarly, both days are moved one day later if Yom Hazikaron would fall out on Sunday.
This holiday honors veterans and fallen military personnel of the Israel Defense Forces who died in the modern Arab Israeli conflict, as well as members of the various paramilitary organization of the Yishuv , such as the Haganah and Irgun, who died before the establishment of Israel, starting from 1860, when the first modern jewish settlement was built outside the walls of the Old City of Jerusalem. Yom Hazikaron also commemorates civilians murdered by acts of terror. As of 2007, Yom Hazikaron honors the memory of over 23,000 people.
The day includes many national ceremonies for fallen soldiers in which senior public officials and military officers are present. The day opens the preceding evening at 20:00 (8:00 pm), given that in the Hebrew calendar system days begin at sunset, with a one-minute siren during which most Israelis stand in silence, commemorating the fallen and showing respect. Many national-religious (religious-Zionist) Jews say prayers for the souls of the fallen soldiers at this time as well. The official ceremony to mark the opening of the day takes place at the Western Wall, at which time the flag of Israel is lowered to half mast.
A two-minute siren is heard the following morning, at 11:00, which marks the opening of the official memorial ceremonies and private remembrance gathering which are held at each cemetery where soldiers are buried. The day officially draws to a close between 19:00 - 20:00 (7-8:00 p.m.) in the official ceremony of Israel Independence Day on Mount Herzl, when the flag of Israel is returned to full mast.
Scheduling the memorial day right before the independence day is supposed to remind people of the price paid for independence and of what was achieved with the soldiers' sacrifice. This transition shows the importance of this day among Israelis, among whom many, if not most, have served in the armed forces or have a connection with people who were killed during their military service.
Historically the date was chosen because during the first year of Israel's existence politicians were not able to agree on a date for a memorial day. As the year came to a close without a decision, the memorial day was celebrated on Israel's first independence day (1949), and the same arrangement was made the following year (1950). Celebrating the holidays together proved difficult (both logistically and emotionally), so in 1951, following the recommendation of a public commission, the memorial day was moved one day back. This arrangement was enacted as a law in 1963.