ibn Shatir designed and built a horizontal sundial that was at the Grand Mosque of Damascus. His sundial was made of marble, 2 meters × 1 meter and was engraved on the marble so that he could read the time of day in equinoctial hours for times of prayer. Also, Ibn al-Shatir made a much smaller sundial. It could be used to find the times of the midday and afternoon prayers. It could also tell him the local meridian and the direction of Mecca.

Replica (created in 1890 CE after the original was damaged beyond repair) of the sundial (inspect), developed by ibn Shatir, atop the Madhanat al-Arus (The Minaret of the Bride) in Umayyad Mosque. The idea of using hours of equal time length throughout the year was the innovation of Ibn al-Shatir in 1371 CE, based on earlier developments in trigonometry by al-Battānī.

circa 850 CE

The sundial is the oldest polar-axis sundial still in existence. Ibn al-Shatir also invented a timekeeping device called "ṣandūq al‐yawāqīt" (jewel box), which incorporates both a universal sundial and a magnetic compass. He invented it for the purpose of finding the times of prayers.

Ibn Shāṭir’s sundial at the Umayyad Mosque is a horizontal instrument engraved on a rectangular marble slab measuring approximately 2 × 1 meters. It was designed to indicate multiple temporal systems: the elapsed hours since sunrise in the morning, the remaining hours until sunset in the afternoon, and time measured relative to local midday. The scale and layout reflect both practical visibility and mathematical precision.

A distinctive and innovative feature of the instrument is its polar-aligned gnomon. Rather than being perpendicular to the dial plate, the gnomon is inclined parallel to the Earth’s rotational axis, forming an angle of approximately 33.5° with the horizontal—corresponding to the medieval value for the latitude of Damascus. This configuration enabled the accurate representation of equinoctial (equal-length) hours throughout the year.

The instrument integrates three distinct but interrelated sundials within a single slab. The southernmost dial, positioned at the upper portion of the slab, measures unequal (seasonal) hours. Its western hour lines indicate the number of hours elapsed since sunrise, while its eastern lines indicate the number of hours remaining until sunset. The effective gnomon for this dial is not an independent structure but the southernmost point of the principal gnomon.

The central sundial constitutes a refinement of the southern dial and provides greater temporal resolution. Like the first, it displays hours since dawn and hours until sunset; however, the spaces between its hour lines are subdivided into intervals of twenty minutes. Its gnomonic reference is the northernmost point of the principal gnomon. In addition, the sloping edge of the main gnomon—rising from south to north—casts a shadow across specific markings on this central dial, thereby indicating equinoctial hours.

To the north of the principal gnomon, Ibn Shāṭir added an auxiliary gnomon, consisting of a vertical post topped with a south-sloping blade inclined at the same polar angle. Positioned just north of the winter solstice line, this auxiliary element extends the shadow of the main gnomon, allowing time to be read in smaller units of approximately four minutes, particularly during periods when the Sun is low.

The northernmost dial, now lacking its original vertical gnomon, was designed to display seasonal hours specific to Damascus. The shadow of the gnomon’s tip would have traced these hours, and this dial also incorporated curves associated with the determination of the afternoon prayer (ʿaṣr).

Several engraved curves across the instrument are explicitly linked to Islamic prayer times. On the eastern side of the dial, seven curves concave toward the midday line are preserved; the outermost of these marks the time of the afternoon prayer. Other curves are labeled with temporal designations, such as “13½ hours until dawn,” indicating time reckoned relative to the daybreak prayer (ṣubḥ). Together, these features demonstrate the integration of astronomical theory, religious practice, and precision craftsmanship in Ibn Shāṭir’s design.

circa 850 CE

Minaret of the Bride (مئذنة العروس), of Masjid al-Umawi as seen from the courtyard of the mosque complex, with dome of the treasury to the left. On one of the slabs it bears the replica of a Sundial built by ibn Shattir, which was used to calculate Salah timings. The 9th-century Arab geographer, al-Muqaddasi, credited the Abbasids for building the northern minaret (Madhanat al-'Arous; "Minaret of the Bride") of the mosque in 831 during the reign of the caliph al-Ma'mun (r. 813–833).