  Octans is one of the most distant ($d\sim150$pc) young stellar associations
of the solar neighbourhood. Its age is still poorly constrained in the
literature and requires further investigation. We take advantage of the
state-of-the-art astrometry delivered by the third data release of the Gaia
space mission combined with radial velocity measurements obtained from
high-resolution spectroscopy to compute the 3D positions and 3D spatial
velocities of the stars and derive the dynamical traceback age of the
association. We performed an extensive traceback analysis using different
subsamples of stars, different metrics to define the size of the association,
and different models for the Galactic potential to integrate the stellar orbits
in the past. We derive a dynamical age of $34^{+2}_{-2}$Myr that is independent
from stellar models and represents the most precise age estimate currently
available for the Octans association. After correcting the radial velocity of
the stars for the effect of gravitational redshift, we obtain a dynamical age
of $33^{+3}_{-1}$Myr, which is in very good agreement with our first solution.
This shows that the effect of gravitational redshift is small for such a
distant young stellar association. Our result is also consistent with the less
accurate age estimates obtained in previous studies from lithium depletion
(30-40Myr) and isochrones (20-30Myr). By integrating the stellar orbits in
time, we show that the members of Octans and Octans-Near had different
locations in the past, which indicates that the two associations are unrelated
despite the close proximity in the sky. Our results confirm that it is possible
to derive precise dynamical ages via the traceback method for $\sim30$Myr old
stellar clusters at about $\sim150$pc with the same precision level that has
been achieved in other studies for young stellar groups within 50pc of the Sun.
