The Time-of-Arrival (ToA) of coronal mass ejections (CME) at Earth is a key parameter due to the space weather phenomena associated with the CME arrival, such as intense geomagnetic storms. Several approaches to estimate the ToA based on kinematical parameters derived from single- and multi-viewpoint white-light coronagraph observations have been proposed and implemented, particularly in the last decade. Despite the incremental use of new instrumentation and the development of novel methodologies, ToA estimated errors remain above 10 hours on average. Here, we investigate the prediction of ToA of CMEs using observations solely from heliospheric imagers, i.e., from heliocentric distances higher than those covered by the existent coronagraphs. To that aim, we analyse 14 CMEs observed by the heliospheric imager HI-1 onboard the twin STEREO spacecraft to determine their front location and speed. Outside the field of view of the instruments, we assume that the dynamics of the CME evolution is controlled by the aerodynamic drag, a force that comes from the interaction with particles from the background solar wind. We found a CME ToA error mean value of 0.4+-7.3 hours ToA and a mean absolute error of 6.1+-3.6 hours in a set of 14 events. The results we found here illustrate that observations from HI-1 allow us to estimate the ToA with similar errors than observations from coronagraphs.