Install alarm-clock-applet by entering the following commands in the terminal:
sudo apt update sudo apt install alarm-clock-applet
alarm clock panel indicator
Alarm Clock is a fully-featured alarm clock which resides in the notification area. It is easy to use yet powerful with support for multiple and repeatable alarms, as well as snoozing and a flexible notification system. . Two types of alarms are supported: Alarm Clocks and Timers. Notification is done by either playing a sound or launching an application.