Abstract: The subject of this research is the analysis of critical approach of the Ottoman scholar Ahmed Efendi Hayati towards attempts to determine precise time of the arrival of Messiah (Mahdi) based on the material of a brief treatise “Mistakes of the Predictors Mahdi’s Arrival”. The object of this research is the concept of “determination of time” commonly used in Islamic philosophical-theological literature for localization of time of arrival of the Messiah. The author demonstrates that the relevance of this topic is substantiated by the fact that it remains extremely important in the Sunnism and Shisim doctrines. The article examines such aspects of the topic as the appearance of signs of Mahdi’s arrival and the Second Coming of Jesus, the Last Judgment, and sources commonly referred to in Islamic tradition for determining the signs of arrival the Second Coming. The following conclusions were made: Islamic theologians determined the time of this event leaning on the doctrinal positions of Sunnism and Shiism; Hayati assumed that time of appearance of the evidence of the Last Judgment and day of arrival of the Messiah is impossible to predict by divination, astrology and horoscope, and that the absence of records of precise time of the event in the Muslim tradition is another proof of failure of the attempts to determine the time of the Second Coming. The novelty consists in the fact that the author is first to analyze the views of Ahmed Efendi Hayati upon the problem of determination of time of Messiah’s arrival.