  We update the ephemerides of 16 transiting exoplanets using our ground-based
observations, new TESS data, and previously published observations including
those of amateur astronomers. All these light curves were modeled by making use
of a set of quantitative criteria with the EXOFAST code to obtain mid-transit
times. We searched for statistically significant secular and/or periodic trends
in the mid-transit times. We found that the timing data are well modeled by a
linear ephemeris for all systems except for XO-2 b, for which we detect an
orbital decay with the rate of -12.95 $\pm$ 1.85 ms/yr that can be confirmed
with future observations. We also detect a hint of potential periodic
variations in the TTV data of HAT-P-13 b which also requires confirmation with
further precise observations.
