Rainlendar - Rainlendar - Customizable desktop calendar
Memo to Me - Online email & SMS reminder service.
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
Date Reminder - Date Reminder reminds you of recurring or nonrecurring events, like birthdays, bills to pay...
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Reminder Commander - Reminder manager that reminds you about important events in advance.