Web-based reservation systems realize a broad variety of different and often inadequate ways of handling temporal data in their user interfaces. We compiled possible procedures for treating temporal data in reservation sys tems in a Morphological Box, ending up with 49 treatment options for 15 fea tures. We initiated an usability inspection by 15 usability experts, asking for evalua tion of the user-friendliness of these options and the relevance of their dif fer ences. After discussing the results we use them to develop an evaluation model. We draw profile lines to compare existing systems, weight the scores of the options by relevance factors of the features, and compute aggre gate usabil ity indicators to rank the systems. In our analysis of 60 airlines, Delta Air Lines and American Airlines reach the best results. We also show that companies that belong to the same group differ remarkably in the usability of their reservation systems.