Timer is a widget for the macOS Dashboard for alerting after a set amount of time has passed. Just type an amount of time, click Start, and it will begin counting down. When it reaches zero, a sound will play and a notification message will appear in the top-right corner of your screen.
Hover your mouse pointer over Timer and click the small "i" to flip to the back side, where you can change various settings.
If you're running OS X 10.10 Yosemite or later, you may need to turn on Dashboard if it isn't on already. On OS X 10.9 Mavericks and earlier, the Dashboard is always on.
Download Timer.zip from this page, then find it on your hard drive and double-click it to open it.
Right-click on the Timer widget icon and select "Open" in the menu. If you don't have a right mouse button, hold the "control" key on the keyboard then click the icon.
Click the "Open" button to confirm that you want to install Timer.
Timer works on Mac OS X 10.5 Leopard through macOS 10.14 Mojave.
OS X 10.8 Mountain Lion or later is required for notification messages to be displayed.
Timer is copyright © 2015 Lucas Bleackley Petter.
Timer is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Timer is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
Credit to third-party software used in Timer: