Highly customizable cross-platform calendar application.
Rainlendar Pro is a feature-rich computer calendar that is lightweight and uses minimal system resources. It stores all the events in the standard iCal format, which makes sharing them with other similar applications possible. You can associate different appearances to different events, add sound alerts to remind you of certain tasks or appointments, and a host of other features.
There is a limited Lite version available for free; see a comparison of the Lite and Pro version here.
Updated on May 16 2022