Desktop iCalendar Lite 

Desktop iCalendar Lite is a free utility that helps you keep track of your daily tasks, create to-do lists, set reminders, and so much more. The application consists of 3 windows: Calendar, Events, and Todos. Keeping them all on your desktop will help you be on schedule at all times and easily manage your daily task data.

This program gives you access to various settings for customizing the appearance of its main screens. For instance, you can change the background image of the aforementioned windows, select another text color, etc. The app also offers you an option to always keep its screens on top of other running programs.

Another useful advantage is that you can create as many calendars as you like. For example, you can build a calendar for office. Add business meetings as events and assignments as to-do items. And you can create a different calendar for personal needs where you can monitor household chores, birthday events, etc.

A disadvantage is that it supports only one audio formats - WAV (audio format supported for importing files for alarm sounds). Another thing that's worth mentioning is that there's a Pro version of the app which provides you with more features (for example, the ability to sync stored data across Google Calendar service), but comes with a price.

Personally, I prefer using this Lite version of the program as it offers me all the features I need. But if you're the kind of user who needs to constantly check calendar details, no matter your location, I'd suggest you to try the Pro version of the app.