On the recommendation of Orlov, who had studied at the Sorbonne, Stoyko was appointed to a position at the Paris Observatory in the Bureau International de l'Heure (BIH).
At the convention, held from the 20th to the 25th of October 1913, representatives from 26 countries approved the creation of a Bureau International de l'Heure (BIH) installed in the premises of the Paris Observatory.
Acknowledgments addressed to Stoyk contained in the annual reports of the Paris Observatory indicate that during WW II he lived in the BIH office to ensure its continuous operation.
[6] For the synchronization of clocks, two astronomical standards were used until 1935: These astral movements were timed at different points on the globe by mechanical instruments derived from the Repsold pendulum.
The first quartz clocks, based on the excitation of a crystal by an alternating electric voltage, used lamp electronics: their size was that of a refrigerator (with a volume of roughly .5 cubic meter); but they allowed a timing regularity of the order of 10 microseconds between two equinoxes.
[7] Equipped with the recordings made with these new clocks located at various places on planet Earth, Stoyko, simultaneously with the German astronomers Adolf Scheibe (1895–1958) and Udo Adelsberger (1904–1992),[8] scientifically described, between 1935 and 1937, a seasonal variation of the daily speed of the rotation of the Earth,[9] which lengthens or shortens the day by 4 milliseconds per decade.
[7] Stoyko and his contemporaries attributed these newly discovered irregularities in the Earth's rotation to the displacement of the atmospheric and mantle masses of the globe, which makes them unpredictable.