How to programmatically read the date when my Android apk was built? [duplicate]

Answer 1

Note 6/1/2020: Android Studio 4.1 Canary 10 w/Gradle >= 6.5 has updated instructions. If you are seeing an "Unsupported BuildConfig type : java.util.Date error, scroll down for the fix.

[Older Instructions]

In build.gradle, each of your build types should have a buildConfigField. (This is a simplified version of the configuration- you're likely to have other stuff in here, but I wanted to show where you put it):

android {
    signingConfigs {
        buildTypes {
            debug {
                buildConfigField "java.util.Date", "BUILD_TIME", "new java.util.Date(" + System.currentTimeMillis() + "L)"
            }
            release { 
                buildConfigField "java.util.Date", "BUILD_TIME", "new java.util.Date(" + System.currentTimeMillis() + "L)"
            }
        }
    }
}    

(Note that "BuildConfigField" is the newer version of "BuildConfigLine" as of the 0.8.0 build system.)

The next time gradle does assembleRelease or assembleDebug, it should generate:

./build/source/buildConfig/releaseORdebug/com/your/project/BuildConfig.java

Next, inside that BuildConfig file, you should see something has been auto-generated like:

public final class BuildConfig {
    public static final java.util.Date BUILD_TIME = new java.util.Date(1395794838381L);
}

So, to access the build date within your app....

Date buildDate = BuildConfig.BUILD_TIME;
Log.i("MyProgram", "This .apk was built on " + buildDate.toString());

(You can format the date however you like using a SimpleDateFormat.)

Update 6/1/2020 -- In Android Studio 4.1 Canary 10 w/Gradle 6.5, the above solution results in an "Unsupported BuildConfig type : java.util.Date" error. A slight variation to the above should be used instead:

android {
    signingConfigs {
        buildTypes {
            debug {
                buildConfigField("String", "BUILD_TIME", System.currentTimeMillis().toString())
            }
            release { 
                buildConfigField("String", "BUILD_TIME", System.currentTimeMillis().toString())
            }
        }
    }
} 

Update 7/30/2020 After gradle 6.6-rc4, you need to include the enclosing quotes for the time by changing to this line:

        buildConfigField("String", "BUILD_TIME", "\"" + System.currentTimeMillis().toString() + "\"")

Inside the BuildConfig file, you should see something has now been auto-generated like:

public final class BuildConfig {
      public static final String BUILD_TIME = "1590735284503";
}

So now, to access the build date within your app....

private Date buildDate = new Date(Long.parseLong(BuildConfig.BUILD_TIME));
Log.i("MyProgram", "This .apk was built on " + buildDate.toString());

As before, you can format the date however you like using a SimpleDateFormat.

Hope this is helpful.