In the current paper, a departure time choice model including travel time variability is estimated, combining stated preference and revealed preference data. We account for response scale differences between RP and SP data and, applying the mixed logit model, test for correlation of scheduling sensitivity across RP and SP choices within individuals. The analysis implies systematic differences in the RP and SP data. With support of the evaluation from the Stockholm trial, this indicates that SP is less trustworthy for trip timing analysis and forecasting, presumably because there are temporal differences in RP and SP choice situations.