To provide a variable camshaft timing system capable of locking a camshaft at several fixing positions.

This system comprises a camshaft 36, a vane 20 comprising lobes 22, 24 and 26 fixed on the same and recessed parts 30, 32 and 34 with having the vane 20 surrounded, of which at least one of the recessed parts has a longer circumferential length than that of at least one of the lobes and receives at least one of the lobes. The system comprises an annular housing 28 capable of vibrating the camshaft 36 and the vane 20, driving means 56, 58 and 68 adapted to make circumferential relative movement between the annular housing 28 and the vane 20, and a locking means adapted to prevent circumferential relative movement between the housing 28 and the vane 20 at one of a plurality of circumferential relative positions of the housing 28 and the vane 20 during a low pressure period of engine oil.