Techniques are disclosed for keeping calendars up-to-date, whereby a person's working hours, events, and actual availability are accurately reflected. In response to user-generated input and/or application-generated input, working hours can be updated and calendar events can be added to, deleted from, or changed on the user's calendar. This makes it easy for users to keep calendars (including working hours) up-to-date and helps both people and applications that use calendar data. Profiles are preferably used to specify working hours, and a particular user may have one or more profiles available (including a default profile); the user can then easily select from among these profiles to update the working hours for a date/day, or a range of dates/days. Preferences may be associated with the profiles, providing a convenient way of isolating information that applies only to a particular set of working hours.