Category
page 1Calendaring software
Microsoft Outlook
email service developed part of Microsoft 365
Google Calendar
time-management and scheduling calendar service
Calendar
personal calendar application for macOS and iOS by Apple Inc.
cal
shell command in various operating systems

MobileMe
MobileMe (formerly .Mac and originally iTools) is a discontinued subscription-based collection of online services and software offered by Apple Inc. All services were gradually transitioned to and eventually replaced by the free iCloud, and MobileMe ceased on June 30, 2012, with transfers to iCloud being available until July 31, 2012, or data being available for download until that date, when the site finally closed completely. On that date all data was deleted, and email addresses of accounts not transferred to iCloud were marked as unused.
Windows Calendar
an application of Microsoft windows

digital calendar
calendar software which can be used to keep track of planned events and appointments
Outlook on the web
Microsoft’s personal information manager web app
Windows Mobile Device Center
synchronization software program
eM Client
email client
Remember the Milk
web-based task- and time-management application
Mail
conflation of two applications developed by Microsoft
Rainlendar
Rainlendar is a calendar program for Windows, Mac OS X and Linux. Versions prior to version 2 are licensed under the GNU GPL as free software, but subsequent versions are proprietary shareware with the paid version costing 9.95 euros.
Nintendo Today!
smart device app from Nintendo