August: Shah Muhammad Reza Pahlavi, who had resisted for months despite British and American calls for him to dismiss Prime Minister Mohammed Mossaddegh, gets nervous about the popular nationalist prime minister's designs when Mossadegh dissolved the parliament and began rule by decree. As a result, the Shah dismisses Mossadegh as prime minister. But Mossadegh refused to step down and instead arrested the royal messenger delivering the dismissal order. In a panic, the Shah flees to Italy. CIA and British intelligence initiate and execute "Operation Ajax" with conservative Iranians to overthrow Mossadegh. Shah returns to Iran.
March 31: Husain Borujerdi, the prominent Marja of all Shi'a, dies. Khomeini emerges as one of the probable successors to Boroujerdi's position of leadership. This emergence was signaled by the publication of some of his writings on fiqh, most importantly the basic handbook of religious practice entitled, like others of its genre, Tozih al-Masael. He was soon accepted as Marja-e Taqlid (source of imitation) by a large number of Iranian Shi'is. In this year his students, who were the teachers of seminary, established Society of Seminary Teachers of Qom, which played key role during establishment of new government after victory of revolution. 
October–November: Khomeini organizes opposition to the Shah's Local council election bill. The Bill introduced by Shah's government allows women to vote for the first time and non-Muslims to run for councils. Religious pressure forces government to back down completely and abandon the bill. Khomeini emerges from fight as "the regime's principal political foe" and "undisputed spiritual leader of ... bazaari activists."
January: Mohammad Reza Pahlavi proposes "White Revolution". The government introduces a six-point reform bill to be put to a nationwide referendum vote. Six points also included Women's suffrage, as well as other reforms.  Khomeini summoned a meeting of his colleagues in Qom to press upon them the necessity of opposing the Shah's plans.
January 22: Khomeini issued a strongly worded declaration denouncing the Shah and his plans. Two days later Shah took armored column to Qom, and he delivered a speech harshly attacking the ulama. Khomeini continues his denunciation of the Shah's programs, issuing a manifesto that also bore the signatures of eight other senior scholars. In it he listed the various ways in which the Shah had violated the constitution, condemned the spread of moral corruption in the country, and accused the Shah of comprehensive submission to America and Israel. He also decrees that the Norouz celebrations for the Iranian year 1342 be canceled as a sign of protest against government policies. Escalating antipathy between Shah and Ayatollah climaxes in June with drawing parallels between the Umayyad CaliphYazid I and the Shah and warns the Shah that if he did not change his ways the day would come when the people would offer up thanks for his departure from the country.
January 24: Shah orders to arrest Khomeini two days later, and major protest riots in cities over Iran the day after that which is called Movement of 15 Khordad. Martial law is declared and hundreds are killed. After nineteen days in the Qasr prison, Ayatollah Khomeini was moved first to the 'Eshratabad' military base and then to a house in the 'Davoudiyeh' section of Tehran where he is kept under surveillance.
April 7: Khomeini is released from custody and returns to Qom. In autumn he denounces "capitulations" (the government's underhanded extending of diplomatic immunity to American military personnel), and calls the agreement as surrender of Iranian independence and sovereignty, made in exchange for a $200 million loan that would be of benefit only to the Shah and his associates, and describes all those in the Majlis who voted in favor of it as traitors, concluding that the government is illegitimate. He is arrested immediately and taken to Mehrabad Airport in Tehran. He's exiled in November, and does not return to Iran for 14 years.
September 5: Khomeini leaves Turkey for Najaf in Iraq, where he was destined to spend thirteen years. He teaches in seminary during this time.
January 21-February 8: Khomeini gives a series of nineteen lectures to a group of his Talaba (students) on Islamic Government while he was in exile in Iraq in the holy city of Najaf. Notes of the lectures were soon made into a book that appeared under three different titles: The Islamic Government, Authority of the Jurist, and A Letter from Imam Musavi Kashef al-Qita (to deceive Iranian censors). The small book (fewer than 150 pages) was smuggled into Iran and "widely distributed" to Khomeini supporters before the revolution.
June 1975: Anniversary of the uprising of 15 Khordad. Students at the Feyziyehmadreseh hold a demonstration within the confines of the building, and a sympathetic crowd assembles outside. Both gatherings continues for three days until they are attacked by military forces, resulting in some casualties. Khomeini reacts with a message in which he declares the events in Qom and similar disturbances elsewhere to be a sign of hope that "freedom and liberation from the bonds of imperialism" is at hand.
January 7: An article in the Ettela'at newspaper by the Information Minister Daryoush Homayoun, titled "Black and Red Imperialism" accuses Khomeini of homosexuality and other "misdeeds". Later in his book, Hun claimed that this was done on the Shah's order.
January 9: Demonstration of 4,000 students and religious leaders in the city of Qom against the article. The armed police was provoked by the angry demonstrators which resulted in death of between 10 and 72 demonstrators.  Protests credited with breaking the "barrier of fear" of security forces "at the popular level". 
February 18: Arbayeen (i.e. 40th day observance) of Qom's fallen protesters.  Groups in a number of cities marched to honour the fallen and protest against the rule of the Shah. This time, violence erupted in Tabriz. According to some reports approximately 100 demonstrators are killed.
March 29: Arbayeen of Tabriz's fallen protesters by demonstrations in various cities. Demonstrators are killed by police in Yazd.
June 20: 40th day cycle of marking demonstration deaths passes with little violence, thanks to calls by Shariatmadari's for observance in mosques not on the streets. Inflation subsiding. Regime's "carrot and stick" and anti-inflation measures seem to be working.
August 6: Shah pledges free elections by June 1979 in broadcast to the nation.
August 19: 477 die in arson fire at Cinema Rex in Abadan. Regime and opposition blame each other.
August 27: Jamshid Amouzegar is replaced by Jafar Sharif-Emami as the prime minister. Sharif Emami "reverses" some of the Shah's policies. Closes casinos (owned by Pahlavi Foundation), abolishes the imperial calendar and declares all the political parties have the right to be active.
September 8: dubbed "Black Friday" Shah declares martial law in response to protests against Pahlavi dynasty. The military of Iran use force including tanks and helicopters to break up the largely peaceful demonstrators. About 88 demonstrators (including three women) are killed. Opposition leaders falsely spread the death count figures as high as "tens of thousands".
September 24: Iraqi government embargoes the house of Khomeini in Najaf and bans his political activities.
October 10: Khomeini takes up residence in the suburb of Neauphle-le-Château in a house that had been rented for him by Iranian exiles in France. He enjoys media attention from journalists across the world who come to France to interview him. His image and words became a daily feature in the world's media.
October 16: Arbayeen of protesters killed on "Black Friday". Some people were killed in the main mosque of Kerman. "A rapid succession of strikes cripple almost all the bazaars, universities, high schools, oil installations, banks, government ministries, post offices, railways, newspapers, customs and post facilities," etc. and "seal the Shah's fate."
November 4: Destructive riots frustrated by Shah's unsuccessful attempts at conciliation with his opponents, military hardliners decide to order troops "to stand aside and allow mobs to burn and destroy to their hearts' content." Thousands of shops, banks, restaurants and other public buildings damaged. Conciliatory Prime Minister Sharif-Emami resigns. Army raid in Tehran University, students participating in demonstrations are killed.
November 5: Shah Mohammad Reza Pahlavi broadcast on television a promise not to repeat past mistakes and to make amends saying, "I heard the voice of your revolution... As Shah of Iran as well as an Iranian citizen, I cannot but approve your revolution."
November 27: Millions throughout the country celebrate "weeping" and "jumping" after seeing Khomeini's face in the moon, after rumour sweeps the land that the Imam's face will so appear on this night. Even the Tudeh Party embraces the story.
December 10 and 11: Tasu'a and Ashura. As many as 17 million people "up and down the country march peacefully demanding the removal of the Shah and return of Khomeini." 17-point resolution is presented during the demonstration "declaring the Ayatollah to be the leader of the Iranian people," and calling on Iranians to struggle until the Shah is overthrown.
December 29: Long-time opposition politician Shapour Bakhtiar was chosen as the prime minister by Shah as the Shah prepares to leave the country. Last prime minister of the Pahlavi dynasty.
January 16: Shah Mohammad Reza Pahlavi and his family leaves Iran for Egypt. Official reports claim that he has left for vacation and medical treatment but in fact he was asked to leave by Shapour Bakhtiar.
February 10: Bakhtiar announces curfew, martial law. Khomeini orders followers to ignore it, and proclaims jihad against army units that do not surrender to revolutionaries. Leftist guerrillas and revolutionaries join rebel troops looting arms from police stations and other government facilities. Army finally declares neutrality to avoid disintegration
February 11: Regime collapses. Revolution victorious. Pahlavi dynasty ends. Royal prime minister, Bakhtiar, goes into hiding, eventually finding exile in Paris.
June 5: Early indication of split between Khomeini and non-theocratic intellectuals. In a speech, Khomeini asked: "Who are they that wish to divert our Islamic movement from Islam? ... Intellectuals, do not be Western-style intellectuals, imported intellectuals."
June 14: Official preliminary draft of the constitution published. Draft constitution contains Council of Guardians to veto un-Islamic legislation, but no Velayat-e faqih (Guardianship of the Islamic Jurists). Khomeini declares it `correct.`
June 15: Khomeini attacks liberal and leftwing groups as `counter-revolutionaries` against Islam. Groups had advocated the election of a Constituent Assembly to write the new constitution. "No `Westernized jurists` are needed to write the constitution, only `noble members of the clergy.`" "Campaign launched to popularised the idea of the velayat-e faqih," hitherto virtually unknown to most Iranians.
June 17: "Construction Jihad" was established by the order of the Ayatollah Khomeini.
August 7: Ayandegan, "the daily newspaper with the widest circulation" in Iran, but "which had agitated against Velayat-e faqih" is banned under new press law for "counter-revolutionary policies and acts."
August 10: Khomeini denounces opponents of the Assembly of Experts and defenders of Ayandegan newspaper calling them "wild animals" and saying, "We will not tolerate them any more ... After each revolution several thousand of these corrupt elements are executed in public and burnt ... We will close all parties except the one, or a few which act in a proper manner ..."
August 12: More demonstrations. National Democratic Front schedules a mass demonstration to protest the closure of newspapers like Ayandegan. Demonstration is "viciously attacked by Hezbollah thugs." Shortly thereafter a warrant is issued for the arrest of Hedayat Matin Daftari, one of the National Democratic Front's leaders. Hundreds are injured by rocks, clubs, chains and iron bars. The next day Khomeini supporters attack and loot offices of leftist groups in retaliation for demonstrations.
September 9: Mahmoud Taleghani, the high rank revolutionary cleric and member of revolutionary council, dies. A friend of the left, Taleghani is considered the second most popular ayatollah after Khomeini.
October 14: Assembly of Experts approves draft of new constitution. In it, Khomeini holds the position of vali-ye faqih, which includes "command of the armed forces" 
October 22: Shah Mohammad Reza Pahlavi is allowed to enter United States for gall bladder treatment. Khomeini speaks out angrily at this "evidence of American plotting." Revolutionary denunciation of the Great Satan (America) intensifies.
November 1: Prime Minister Bazargan photoed shaking hands with U.S. official Zbigniew Brzezinski at a meeting in Algeria. Radical leftist and theocratic media in Iran alerts the "nation of the return of American influence."
November 4: Aggressive demonstrations take place near the Embassy of the United States. Embassy awaits instructions from Washington D.C. Hostage crisis takes place in the morning: 500 demonstrators climb over the Embassy’s fence as the Iranian Police look on. The attack was planned before. Embassy clerks ask for help from the Iranian government which does not come as promised. Embassy guards defend the compound with tear gas because firearms are permitted for use. Secret documents are burned in the Embassy. About ninety people are taken hostage of which 66 are Americans.
November 5: Iranian government cancels all defence treaties with the United States and Soviet Union.
November 6: Mehdi Bazargan, prime minister of The Interim Government of Iran, resigns, "unable to muster" support for "eviction of the students." Khomeini immediately accepts his resignation along with all the other members of his cabinet.
November 7: U.S. president Jimmy Carter's appointed delegation arrives to Iran to negotiate to free the hostages.. Members of the delegation are former federal judge Ramsey Clark and William Miller with the intent to negotiate the end of the hostage crisis. Ayatollah Khomeini refuses to see the delegation.
November 12: Iranian Foreign minister Abolhassan Banisadr informs that the hostages will be released if U.S. deports the Shah back to Iran.
November 14: U.S. Government freezes the all property and interests in the property of the government of Iran and the Central Bank of Iran.
December 2 and 3(11th and 12th of Azar): New Constitution of Iran was approved by referendum by over 98 percent of the vote,  but much lower turnout because of boycott. Khomeini becomes vali-ye faqih.
December 15: Shah Mohammad Reza Pahlavi leaves the U.S. for Panama
December 16: Shah Mohammad Reza Pahlavi arrives to Panama
March 12: Iranian government demands that the Panamanian government arrest the Shah Mohammad Reza Pahlavi 
March 15: First round of elections of first Islamic parliament. Islamic Republican Party mobilises its network among clergy, komitehs and the revolutionary guard. Hezbollah attacks rallies and offices of opposition parties, primarily the Mojahedin-e Khalq, as most other parties have been effectively repressed.
March 21: Cultural revolution begins. In New Year's speech, Khomeini inveighs against "imperialist universities" where those "cloaked with the West" teach and study. Declares the universities must "become Islamic." 
March 23: Shah Mohammad Reza Pahlavi leaves Panama to return to Egypt.
March 25: Shah Mohammad Reza Pahlavi returns to Egypt
April 25: Operation Eagle Claw;Tehran hostage rescue mission fails with the death of eight U.S. soldiers because of sand storm. Khomeini credits divine intervention on behalf of Islam. His prestige is greatly enhanced. Banisadr's is further reduced.
April 27: Demonstration lead by People's Mujahedin of Iran in Tehran draws 150,000. Chief prosecutor bans the Mujahedeen from demonstrating.
August: Banisadr forced to accept Mohammad-Ali Rajai as prime minister. Banisadr considers Rajai to be "incompetent", but Rajai has the support of the Islamic Revolution Party.
12 September: Khomeini puts new terms to release the hostages; U.S. has to release all of the Shah’s currency assets from his American bank accounts. According to the Iranian government, the worth of the foreign assets are about 32 billion U.S. dollars.
September 22: Iran–Iraq War starts. Massive invasion of Iran by Iraq following border skirmishes and a dispute over the Arvand Rūd (Persian: اروندرود, literally Arvand River) or as it is known in Iraq the Shatt al-Arab (Arabic: شط العرب, literally Coast/Beach of the Arabs) waterway. Marks beginning of a war that will last eight years.
January 19: Algiers Accords, between Iran and the United States, mediated by Algeria, to resolve an Iran hostage crisis. In exchange for the release of the hostages by Iran, the United States agreed to unfreeze US$8 billion of Iranian State assets from American banks.
January 20: Ronald Reagan is inaugurated as president of the USA: Only 20 minutes from Reagan’s oath, Iran releases all 52 hostages who are flown to West Germany via Algeria where former U.S. president Jimmy Carter takes them back to the United States. USA conceded to transfer money, as well as export military equipment to Iran.
↑ Kayhan, 20.8.78-21.8.78,` quoted in Schirazi The Constitution of Iran, (1988), p.51) (New York Times)
August 8: demonstrators gather in Tehran to protest closing of Ayandegan. In the next three days 41 newspapers and periodicals are banned under the press law. (Kayhan 20.8.78-21.8.78, quoted in Schirazi The Constitution of Iran, (1988), p.51
↑ From a speech before the delegates of the Assembly of Experts, quoted in Moin Khomeini (2000), p.219