There will be two files "Stopwatch.jar" and "Timestamps.txt" which you have to download. To open the .jar file you need Java Development Kit (JDK) on your PC. To download this, click on this link : https://www.oracle.com/in/java/technologies/javase-jdk15-downloads.html and download the required version of JDK 15.0.2 for your OS. Now, put this .jar file as well as the .txt file into a folder on your PC. And start the application by clicking on the .jar file. There will be a test Timestamp named "testTimestamp" with time set to 00 : 00 : 00 : 00 which you can check out. For developers, I have added .java files which have the source codes as well as .form files which have GUIs.