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Pro Weather, moon-phases and graphics
Display a live 10-day weather forecast and moon phases. Drag-n-drop images into your calendar with the Graphics palette. Customize event fonts, sizes, styles and colors.
Pro Custom Alarms and Snoozes
Alarms may displayed in the BusyCal Alarm Window or the Notification Center. Snooze alarms for any duration, including x minutes before start, Set default alarm intervals for new Events, To Dos, All-Day Events, and Birthdays & Anniversaries.
Pro Smart Filters
Create Smart Filters to display Calendar Sets, a custom view, or events that match a certain criteria with a single click.
Pro Custom number of days/weeks
You can customize the number of weeks shown per month, or days shown per week
Pro Sync with OwnCloud and others
Connections are more stable than in Calendar.
Pro Great support and development team
Pro Integrated To Dos
To Dos can be displayed directly in your calendar and carry-forward until completed. To Dos in BusyCal are compatible and sync with the Reminders app on OS X and iOS.
Pro Latteral bar
Con OSX and iOS Only
Keeps you tied into the Apple ecosystem, not that it's a con, just an observation.