Israel Summer Time (Hebrew: שעון קיץ, romanized: She'on Kayits, lit. 'Summer clock'), also known in English as Israel Daylight Time (IDT), is the practice in Israel by which clocks are advanced by an hour, beginning on the Friday before the last Sunday of March, and ending on the last Sunday of October.

The origin of Israeli Summer Time lies in the period of the British Mandate. In May 1940, the Palestine Government issued the Time Determination Ordinance, which said:

During such period in each year as the High Commissioner may by order prescribe, the time for legal and general purposes in Palestine shall be three hours in advance of Greenwich Mean Time.

The time change first occurred from June 1 to September 30, 1940, and then from 17 November 1940 through all of 1941 until 31 October 1942. Summer Time in 1943 and 1944 was from April 1 to October 31, and in 1945 and 1946 it was from April 16 to October 31. There was no Summer Time in 1947.

The Time Determination Ordinance was inherited by Israel as part of the default adoption of Mandatory Law. Two days after the Declaration of Independence, the provisional government introduced double Summer Time in Jerusalem to save fuel, extending this to the whole of Israel from May 23. Because the shift of two hours violated the Time Determination Ordinance, the change was retrospectively legalized by the Time Determination (Amendment) Ordinance of 3 June 1948, which added "or such other period of time as may by order be prescribed" after "three hours". The two-hour time shift was reduced to one hour from 1 September 1948 and removed altogether from 1 November 1948.

The length of Summer Time has changed significantly depending on the year. In 1951–1952, it was enacted for about seven months, whereas in the years 1953–1954 it was enacted for only three months. In 1958, Summer Time was canceled. Due to the global energy crisis because of the aftermath of the Yom Kippur War, Summer Time was enacted again from 1974–1975.

Up until 1992, daylight saving time was operated by an order of the minister of the interior. In 1980 the authority of the minister for this matter was contested in an appeal to the supreme court. The supreme court decided that the minister's authority was indeed more limited than the common practice, as he may only decide on the dates of IDT while its operation is unquestionable. Following this decision the Knesset amended the Time Act so the minister will also have the authority to abolish IDT in a certain year.

The Law of Determining the Time (Hebrew: חוק קביעת הזמן Hok Kvi'at Hazman) is an Israel law governing Israeli daylight saving time. It was approved by the Knesset in 1992, replacing the Time Determination Ordinance which was inherited by Israel from the Mandate period. The 1992 time zone law stipulated that IDT will be operated for at least 150 days each year, and that the final dates will be decided by the minister of the Interior, subject to the approval of the Knesset committee for internal affairs. In some years the decision as to which day summer time would start or end was made at the last minute due to political haggling and this caused disruption to international airline schedules at Ben Gurion Airport.^{[citation needed]}