Fixed years was the term used in Russian documents for the statute of limitations

Statute of limitations

A statute of limitations is an enactment in a common law legal system that sets the maximum time after an event that legal proceedings based on that event may be initiated...

 during which a run-away serf could be sought out and returned to his landlord. They were fixed at five years by an ukaz (decree) of Tsar Fedor Ivanovich

Feodor I of Russia

Fyodor I Ivanovich 1598) was the last Rurikid Tsar of Russia , son of Ivan IV and Anastasia Romanovna. In English he is sometimes called Feodor the Bellringer in consequence of his strong faith and inclination to travel the land and ring the bells at churches. However, in Russian the name...

 issued on November 24, 1597. They were done away with as part of the Ulozhenie of 1649

Sobornoye Ulozheniye

The Sobornoye Ulozheniye was a legal code promulgated in 1649 by the Zemsky Sobor under Alexis of Russia as a replacement for the Sudebnik of 1497 introduced by Ivan III of Russia, which is based, among others, on the Third Statute of Lithuania...

, where there was no limit on the time a serf could be sought out and returned to his estate.