Calendars can be created with widely available clients such as:
* [http://www.apple.com/macosx/features/ical/ Apple iCal], for Mac OS X:<br />[[Image:ical2.jpg|iCalframeless]] [[Image:ical1.gif|iCalframeless]]* [http://www.mozilla.org/projects/calendar/ Mozilla Sunbird and Lightning (a perfect calendar companion for Thunderbird)], for Windows, Mac and Linux.<br /> attachment[[Image:sunbird.png <br> attachment|frameless]] [[Image:lightning.png|frameless]]
* [http://www.microsoft.com/windows/products/windowsvista/features/details/calendar.mspx Windows Calendar], for Windows Vista.
attachment[[Image:vista-calendar.jpg|frameless]]
* [http://www.gnome.org/projects/evolution/ Evolution], for Linux
attachment[[Image:evolution.png|frameless]]
* [http://http://www.kontact.org/ Kontact], for Linux
attachment[[Image:kontact.jpg|frameless]]
* ... and some others. Pretty soon there will also be web-based interfaces.