We determine new linear ephemerides of transiting exoplanets using long-cadence de-trended data from quarters Q1 to Q17 of the Kepler mission. We analysed transit-timing variation (TTV) diagrams of 2098 extrasolar planets. The TTVs of 121 objects were excluded (because of insufficient datapoints, influence of stellar activity, etc.). Finally, new linear ephemerides of 1977 exoplanets from the Kepler archive are presented. A significant linear trend was observed on TTV diagrams of approximately 35% of the exoplanets studied. Knowing the correct linear ephemeris is key for successful follow-up observations of transits. Residual TTV diagrams of 64 analysed exoplanets show periodic variation, and 43 of these TTV planets were not previously reported.