Google Calendar is a free, Web-based calendar. Users can add events in multiple calendars and access them on their mobile phone or using Google's Gmail. Like many other Google applications, Google Calendar has a collaborative nature. Users can share and subscribe to one another's calendars or import them from third-party services that offer things such as national holidays, movie releases, or moon cycles.
In addition to a calendar view that can be toggled by day, week, or month, you can also create your own custom view that lists anywhere from two days to four weeks. To keep track of any upcoming events, there's also an agenda view that lists everything that's on your calendar in a chronological and color-coded view.
Winner: Google Calendar (Google.com/Calendar)