  We aim to study the phase spiral in the Milky Way (MW) with Gaia DR3. We used
an edge detection algorithm to find the border of the phase spiral, allowing us
to robustly quantify its shape at different positions and for different
selections. We calculated the time of onset of the phase-mixing by determining
the different turns of the phase spiral and using the vertical frequencies from
commonly used MW potential models. We find that the phase spiral extends down
to $-1.2$ kpc in height below the plane (about 3 to 5 scale heights of the thin
disc) and beyond $\pm 50$ km/s in $V_Z$. We see a secondary branch mostly at
positive vertical velocities when coloured by azimuthal velocity and in the
counts projection. We also find complex variations of the phase spirals with
angular momentum and azimuth. All these possibly provide evidence of multiple
perturbations (from different times or from different perturbers) and/or of the
complexity of the phase mixing process. We detect the phase spiral from 6 to 11
kpc from the Galactic centre and find signatures of vertical asymmetries 1-2
kpc beyond this range. We measure small but clear variations with azimuth. When
we determine the phase mixing times from the phase spiral at different angular
momenta and using the different spiral turns (at different $Z$) we obtain
inconsistent times with systematic differences (times increasing with $|L_Z|$
and with $|Z|$). Our determinations are mostly in the range of [0.3-0.9] Gyr,
with an average of 0.5 Gyr. The inconsistencies do not change when using
different usual potential models, different stellar distances or frequencies
for different kinetic temperatures. They could stem from the inconsistency of
potential models with the true MW, and from too simple modelling, in particular
neglecting self-gravity, not considering the multiple perturbations and the
interference with other processes.
