  We present 33 transit minimum times of 20 transiting planets discovered by
the CoRoT mission, which have been obtained from ground-based observations
since the mission's end in 2012, with the objective to maintain the ephemeris
of these planets. Twelve of the observed planets are in the CoRoT fields near
the galactic center and the remaining eight planets are in the fields near the
anticenter. We detect indications for significant transit timing variations in
the cases of CoRoT 3b, 11b, 13b, 27b. For two more planets (CoRoT 18b and 20b)
we conclude that timing offsets in early follow-up observations led to
ephemeris in discovery publications that are inconsistent with timings from
follow-up observations in later epochs. In the case of CoRoT-20b, this might be
due to the influence from a further non-transiting planet. We also note that a
significant majority (23 of 33) of our reported minimum times have negative O-C
values, albeit most of them are within the expected uncertainty of the
ephemeris.
