A desirable activity-based travel demand modeling framework should be able to address both weekday and weekend activities. However, a literature review shows previous research efforts have mostly focused on investigating weekday but not weekend activities. Little or no research exists to quantify the differences between weekend and weekday activities. The best knowledge to date is limited to weekday and weekend activities starting at different time of the day and with different participation rates. This study aims to fill the gap by studying the differences between weekday and weekend activities in Calgary, Canada, in terms of their participation rates, starting time, duration and inferred location choices. First, statistics of these attributes were computed for 10 types of weekday and weekend activities and they were found different. Secondly, Log-rank and Wilcoxon tests further proved a common type of weekday and weekend activity tend to follow different survival functions. Third, best-fit duration models were explored for each type of weekday and weekend activity and compared with each other. It was found that Lognormal and Weibull were chosen as the best-fit models for nearly all weekday and weekend activities. The best-fit duration models for same types of weekday and weekend activities (e.g., shopping) were different in either underlying distribution or estimated parameters. This study clearly shows the weekend activities are different from their weekday counterparts and suggests that they should be treated separately in activity-based modeling frameworks (237 words).