Emacs/docs/latest/emacs/Diary

From Get docs

31.10 The Diary

The Emacs diary keeps track of appointments or other events on a daily basis, in conjunction with the calendar. To use the diary feature, you must first create a diary file containing a list of events and their dates. Then Emacs can automatically pick out and display the events for today, for the immediate future, or for any specified date.

Although you probably will start by creating a diary manually, Emacs provides a number of commands to let you view, add, and change diary entries.

Format of Diary File    Entering events in your diary.
Displaying the Diary    Viewing diary entries and associated calendar dates.
Date Formats    Various ways you can specify dates.
Adding to Diary    Commands to create diary entries.
Special Diary Entries    Anniversaries, blocks of dates, cyclic entries, etc.
Appointments    Reminders when it’s time to do something.
Importing Diary    Converting diary events to/from other formats.