Rainlendar - Rainlendar - Customizable desktop calendar
Date Reminder - Date Reminder reminds you of recurring or nonrecurring events, like birthdays, bills to pay...
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
GoGetter - GoGetter is a task management system based on David Allen’s ever so popular Getting Things Done...
todoMini - Your web based TODO list.
Reminder Commander - Reminder manager that reminds you about important events in advance.