Published by Kültür A.Ş., the cultural enterprise of the Istanbul Metropolitan Municipality, "Istanbul Muvakkithaneleri" (Istanbul's Timing Rooms) delves into the historical development of special places where calendars, clocks and other time-keeping devices are measured. Written in Turkish by Server Dayıoğlu, the recently published book focuses on timing rooms also mentioned in Ahmet Hamdi Tanpınar's masterpiece "Saatleri Ayarlama Ensititüsü" (The Time Regulation Institute), which is a Penguin classic. The books examine different subjects such as instruments that were used in timing rooms and astronomical measurements. Additionally, it informs readers on how iftar (the evening break-fast meal) and sahur (the meal eaten before fasting) times are determined. "The measurement of iftar and sahur times during Ramadan is important, as fasting must be observed according to religious rules. Staff from a timing room used to inform an imam of the iftar time, who then lit up the minaret. Another person would fire the iftar cannon. Timing rooms were measured in the same way. Imams who hear the sound of the cannon would then recite the ‘adhan' [the call to prayer]," wrote Dayıoğlu.During the Ottoman Empire, these timing rooms were established in certain public buildings called "imarets." Nearly all cities and towns had one or two timing rooms located in a mosque or mascid gardens. These establishments were managed by the foundation of a social complex to which they belonged, and their staff was called "muvakkit" (a person measuring time)." Such establishments became popular following the conquest of Constantinople, and it was possible to come across a timing room in every corner of Istanbul. The Ottoman-era timing rooms both functioned as observatories and astronomy training centers. Certain timing rooms trained "munajjimbashi," the head astronomers responsible for informing the sultan about auspicious days based on astronomical measurements. They lost their popularity when clock towers began being built in squares and especially when mechanical clocks were invented during the time of Sultan Abdülmecid I. However, there were some Istanbul gentlemen who continued to visit the timing rooms to have their clocks checked. With the proclamation of the Republic of Turkey, a new establishment, "Başmuvakkitlik" (the chief timing room), was opened to control all other timing rooms; however, they were shut down on Sept. 20 in 1952. Today, certain buildings with timing rooms still survive, but most of them have fallen into neglect or are used for different purposes.