There are several methods to know when an app was downloaded-
1. Go to Settings -> Click on App Info -> Click on the desired App Name
You can see the date when this app was installed in the ‘Data Used’ column. It will display something like “xx MB used since DDMM”
1. Install any of the following Apps to see info about when a particular app was installed on your phone-
AppMonster Free Backup Restore – Android Apps on Google Play
Titanium Backup ★ root – Android Apps on Google Play
Changelog Droid – Android Apps on Google Play
App Detective – Android Apps on Google Play
1. Enable USB Debugging on your phone from the developer options.
2. Set up ADB on your PC
3. Connect your phone to your PC and execute the following commands in command prompt-
I) adb shell dumpsys package
From the result of this command, select the desired package name (of the desired app).
II) adb shell ‘dumpsys package
It will display the date and time when that app was first installed on your phone