Lazar from Hilandar, (also known as the Lazar from Serbia), was born in the town of Prizren, in the second half of the 14th century, but the precise year of his birth is not known. He was a monk wearing a black robe in Hilandar at the Holy Mountain, but probably at the time after the battle of Kosovo he went to Moscow, at the Court of Vasilij I, Great Duke of Moscow and Vladimir. At his orders, in 1404, he projected, elaborated and established the first mechanical clock in Russia, which was at the same time the first and the only clock in this country.
The clock was situated at one of the towers of the Duke Palace, in the vicinity of the church of the Holy Annunciation. It was mechanically driven, by ways of springs and weight, and the strokes of hammer indicated full hours and their quarters, while at the face of the clock, instead of the numbers, there were letters of the church Slovenian alphabet.
Although Lazar did not invent the whole construction, one should bear in mind that in the mentioned period there were very few masters (called artists) that manufactured clocks completely independently and each one of them introduced his own innovations in the previously existing constructions.
Chronologically observed, it is considered that the Lazar Clock is fourth in the line, and in any case, it belongs to the group of ten technologically superb clocks of this time.
Lazar Clock worked without stopping for 217 years altogether, when it was replaced with a new one. Lamentably, the tower where it had been positioned was later destroyed in a fire, so it is only assumed where exactly it had been positioned.