Very Long Baseline Interferometry experiments require an extremely
precise synchronization between the atomic clocks keeping the time
and frequency standards at radiotelescope observatories. Recently the
availability of fiber optic links from a few radio observatories and
their national metrological institutes has made possible the
streaming of extremely stable frequency standards via optical atomic
clocks (even two order of magnitudes better than Rubidium or Hydrogen
maser standards). Firstly, I will present the infrastructure of the
Italian Link for Frequency and Time (LIFT) and results of the MetGesp
project aimed at finally creating a common clock between two of the
antennas of the VLBI Italian Network. Secondly, I will show the
results of VLBI experiments in which the phase rms noise was used to
accurately compare the synchronicity of atomic clocks located at a
few EVN sites (Medicina, Noto, Yebes, Torun).
VLBI clock timing proves a valid alternative to satellite-based
techniques such as Global Navigation Satellite System or Two-Way
Satellite Frequency and Time Transfer.