If your idea of a desktop calendar is a stack of paper you can write notes on as opposed to a trifold organizer or day book, Rainy's Rainlendar Lite is probably your calendar. It's largely unobtrusive and transparent, like a widget, though you can customize its look. But unlike a simple calendar widget or gadget, Rainlendar Lite is also a personal manager that can remind you of tasks and important events. It's fully compatible with most other iCalendar apps, so you can import and export data such as events. You can back up your calendar and even print it out if you miss scribbling on paper. We tried Rainlendar Lite for 64-bit Windows.
Rainlendar is a calendar, of course, so that's what it looks like on the desktop. It showed up with white lettering on our black background, with weekends in pink and the current date circled in red. It also shows the year in small numerals at the bottom. You might think that's not necessary (and, like all of Rainlendar's interface, you can change it) but it's probably needed more than you'd think, and not just by people who suddenly awaken from comas (or those who just don't pay very close attention to stuff). It helps if you're taking screenshots, for example. Rainlendar also has two independent counters, one for Events and another called To Do. These can be dragged and placed independently of the calendar and each other. We really like that capability: Though they're small, the ability to tuck them wherever you need (like the no man's land between the top of your browser window and the top of the screen) makes them extra-versatile. Rainlendar also displays the current date in a System Tray icon. We recommend clicking Show Hidden Icons, then Customize, and making Rainlendar's icon permanent in the notification area; partly because it's a date display but also because the tray icon accesses Rainlendar's settings and features, including new Events and Tasks, the Manager tool, and which of the many customized calendars you can create with Rainlendar to use.
Rainlendar Lite is a top calendar app that'll do well on many desktops.