Holidays in Turkey

Official national public holidays. Regional and religious observances may vary by area.

About Time in Turkey

When Sunset, Not Midnight, Reset the Clock

For much of the Ottoman period, everyday time was organized around a system fundamentally different from the fixed civil clock used today. In the alaturka, ezânî or gurûbî system, sunset was the daily reference point. When the Sun disappeared below the horizon, clocks were adjusted to 12, and a new daily cycle began. Because sunset moves through the year, a mechanical clock keeping uniform hours could not simply be left untouched. Its indication had to be corrected regularly to remain synchronized with the changing solar reference.

This made timekeeping an applied branch of astronomy. Muvakkits, specialists responsible for determining prayer times, worked in purpose-built muvakkithanes associated particularly with important mosques and religious complexes. They used observations of the Sun together with instruments such as quadrants and astronomical tables to establish the required times. Large pendulum clocks eventually became common in these rooms, but the mechanical clock did not eliminate astronomical observation. The clock itself had to be checked and adjusted against the celestial reference.

The nineteenth century created an unusual period in which two concepts of time coexisted. Alaturka time remained anchored to sunset, while alafranga time followed the fixed-hour European system increasingly required by diplomacy, commerce, railways and international communications. Research on surviving Ottoman palace clocks documents double-dial mechanisms capable of showing both systems simultaneously. A single object could therefore display two valid readings of the same instant, one belonging to a solar and religious rhythm, the other to an increasingly standardized international one.

The transition was gradual rather than a clean replacement on a particular morning. Government offices, transport systems, religious institutions and private households did not all abandon the older convention at once. This is one reason late Ottoman documents containing a clock time can require contextual interpretation. A written hour may not be fully meaningful unless the reader knows whether it refers to alaturka or alafranga reckoning.

Thirteen Calendar Days Disappeared in 1917

The reform of daily clock time was only one part of a much larger problem: several calendar systems were also in use. The Rumi calendar had become important in Ottoman fiscal and official administration. It was a solar calendar whose year numbering ultimately derived from the Hijri era, but its day structure had followed the Julian calendar. By the beginning of the twentieth century, the Julian and Gregorian calendars differed by thirteen days.

A 1917 reform removed that discrepancy in a particularly visible way. Under Law No. 125, 15 February 1332 in the Rumi calendar was followed by 1 March 1333. The dates corresponding to 16 through 28 February were therefore omitted from the official Rumi sequence. From that point, its month and day structure was aligned with the Gregorian calendar.

The same reform also changed the shape of the year. Rumi year 1333 began on 1 March 1917 but ended on 31 December, making it only ten months long. Beginning with 1 January 1334, which corresponded to 1 January 1918, the official year started in January rather than March. The old Rumi year number nevertheless remained in use for several more years.

The final step came with Law No. 698 of 26 December 1925. It adopted the international calendar era for the official state calendar. The law specified that the day following 31 December 1341 would be 1 January 1926. This was not another thirteen-day correction. The Gregorian day and month system had already been aligned in 1917. The 1925 law replaced the remaining Rumi year numbering with the international year numbering still used in official civil life.

The legislation explicitly left room for the Hijri lunar calendar in specific contexts. That distinction matters historically because the reform did not erase religious chronology. It separated the official civil calendar from other systems whose months and observances were determined according to different astronomical rules.

Another 1925 Law Redefined the Day Itself

Calendar reform was accompanied by an equally important clock reform. Law No. 697, adopted on the same date as the calendar law, stated that the civil day begins at midnight and that hours are counted from zero to twenty-four. It also established the meridian at 30 degrees east of Greenwich, passing near İzmit, as the basis for clocks throughout the Republic. In modern terms, that meridian corresponds to UTC+2.

This legal wording captures the transition from several older concepts at once. The beginning of the day was now fixed at midnight rather than sunset. Hours belonged to a continuous 24-hour system rather than two twelve-hour cycles dependent on solar observation. A single reference meridian applied nationally, making legal time independent of the longitude of an individual town.

Istanbul had already moved toward zone time before the republican legislation. Historical IANA data reconstructs Istanbul Mean Time as UTC+1:56:56 until October 1910, when the city moved to Eastern European Time at UTC+2. The correction was only 3 minutes and 4 seconds because the 30-degree-east zone was already an excellent geographic fit for Istanbul. The later law gave the system a nationwide legal foundation and explicitly defined the structure of the civil day.

The paired laws of 1925 are therefore best understood together. One standardized how the year was numbered, while the other standardized how each day was divided and referenced geographically. They converted calendar dates and clock readings into conventions that could operate cleanly within international transport, commerce, administration and communications.

The Modern Clock Is One Hour Farther East Than the 1925 Standard

For decades, the basic standard remained UTC+2 with seasonal advances to UTC+3 during periods when daylight saving was in force. That pattern ended in 2016. Government Decision No. 2016/9154 ordered the summer-time arrangement that had begun on 27 March to continue throughout the year and cancelled the scheduled clock change of 30 October. Instead of returning to UTC+2 for winter, clocks stayed at UTC+3.

The arrangement was subsequently placed on a continuing basis. Presidential Decision No. 139, published in October 2018, specified that the existing GMT+3 advanced-time system would remain in force every year throughout the year. The practical result is the system used today: one national time zone at UTC+3 and no spring or autumn clock changes.

Geographically, the difference from the older system is substantial. UTC+2 is centered on the 30th meridian east, the reference explicitly written into the 1925 law. UTC+3 corresponds geometrically to the 45th meridian east. The latter runs near the eastern edge of the country, while Istanbul lies close to 29 degrees east. Civil time is consequently much farther ahead of solar time in western regions than in the far east.

The old Istanbul Mean Time provides a precise way to see the effect. Its historical offset was UTC+1:56:56. Compared with the modern UTC+3 clock, the difference is 1 hour, 3 minutes and 4 seconds. Mean solar noon in Istanbul therefore falls, on average, a little after 1 p.m. by the modern civil clock rather than close to 12:00. Apparent solar noon moves around that average during the year because of the equation of time.

This east-west effect is unavoidable in a geographically wide country using one fixed time zone. A national clock is designed primarily to synchronize people and systems, not to guarantee that the Sun reaches its highest point at 12:00 in every city. The 1925 and 2016 arrangements simply made different choices about where that compromise should fall.

Kandilli Carried Time From the Sky to the Telegraph Network

The history of precise national time can also be followed through the Kandilli Observatory. When systematic work began there in the early twentieth century, the observatory did not merely study astronomy and weather. Its staff adjusted chronometers using astronomical observations and communicated correct time to institutions including the postal and telegraph administration and the state railways.

The basic method still depended on Earth's rotation. A sextant or transit instrument could be used to establish when known celestial objects crossed particular reference positions. Precision clocks then preserved that astronomically determined time between observations. In 1924, observatory director Fatin Gökmen was already proposing equipment and facilities specifically for the precise determination and preservation of time.

The technical infrastructure became progressively more sophisticated. An Askania meridian transit instrument was obtained in 1927, a zenith telescope followed in the 1930s, and later equipment included quartz clocks, comparison oscilloscopes, chronographs and a Danjon astrolabe. The dedicated Time Service continued observational work until the 1970s. Its development documents the period when an observatory was simultaneously a scientific institution and part of the infrastructure needed to keep public systems synchronized.

This was a fundamentally different model from modern network time. Correct time first had to be extracted from astronomical observations, stored in high-quality clocks and then distributed through communications systems. Yet the basic problem is unchanged: railways, communications networks and institutions cannot function efficiently if every clock is allowed to drift independently.

National Time Now Comes From Atomic Clocks, and One Has Gone Into Orbit

Precision time is now maintained by TÜBİTAK UME, the National Metrology Institute. Its Time, Frequency and Wavelength Laboratory generates UTC(UME), the national realization of Coordinated Universal Time. The laboratory's current infrastructure includes five cesium atomic clocks, a hydrogen maser and satellite time-transfer equipment. Since 1994, its measurements have contributed to the international system used in the calculation of atomic time and UTC.

This changes the physical basis of the national reference. Kandilli once determined time by watching Earth rotate beneath the sky. Atomic time instead depends on extremely stable atomic transition frequencies. Satellite links and international clock comparisons connect UTC(UME) with other national laboratories and with the Bureau International des Poids et Mesures. The resulting reference can be distributed electronically through services such as Network Time Protocol, allowing computers to synchronize directly with a traceable national time scale.

The next step moved part of that work off the planet. On 7 July 2026, a domestically developed Rubidium Atomic Frequency Standard, known as RAFS, was launched aboard a 6U CubeSat on SpaceX's Transporter-17 mission. The Turkish Space Agency, TÜBİTAK UME, TÜBİTAK UZAY and Istanbul Technical University participated in the program. Successful communications and telemetry were received after launch, and the payload entered an extended period of testing in low Earth orbit.

The purpose is more demanding than simply keeping a spacecraft clock accurate. Satellite navigation is fundamentally a time-measurement technology. A receiver calculates distance from the travel time of radio signals, so errors of tiny fractions of a second translate directly into positioning errors. Developing a space-qualified atomic frequency standard is therefore a prerequisite for more independent regional positioning and timing capability.

The RAFS mission creates a remarkable historical contrast. Earlier specialists reset mechanical clocks from the Sun, Kandilli later maintained time through astronomical instruments and precision chronometers, and modern metrology compares ensembles of atomic standards through satellites. In 2026, a locally developed atomic frequency reference itself became the payload of a satellite. The technologies are separated by centuries, but every stage addresses the same underlying problem: how to define an interval precisely, preserve it reliably and make distant systems agree on the same instant.

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