Can be a sign to the expiration keystore, install are also available.
ex) 1 day keystore generate.
$ keytool -genkey -v -keystore my-release-key.keystore
-alias alias_name -keyalg RSA -keysize 2048 -validity 1
ex) my-release-key.keystore already is expired.
$ jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1
-keystore my-release-key.keystore my_application.apk alias_name
App launch is also available. So, What is the meaning of the keystore validity in Android?
keystore is used to validate developer's id,that is even the keystore has expired the application will work well on our android phone,it won't impress any functions about this app,but once the developer want to publish new version of this app,it can't use this keystore anymore,otherwise it will be refused by Google play,and if you use a new debug keystore to run on your device for debug,system will informs that pre app will be removed to install new one because they are not compat.