Microsoft Office Outlook, Google Calendar, aCalendar, Fantastical, Notion Calendar, Apple Calendar, Cozi, Morgen, Fossify Calendar, Lightning Calendar, wtplan, CalenGoo, Calendar 366, GroupCal, MeetingBar, Simple Calendar, Superpowered, Itsycal, Attendexer, Pagico, GMinder, Google Calendar Checker, GMX Calendar, ChronoFlo Calendar, MemoCalendar.net, Caliander, vircorX, HipCal, 1calendar, Calvetica, KeepTime, AnCal, Calendarific are some alternatives to BusyCal.