android {

    ...

    buildTypes {
        release {
            minifyEnabled true
            ...
        }
        debug {
            minifyEnabled false
        }
    }

    productFlavors {
        prod {
            applicationId "com.example.myproject"
            versionCode 3
            versionName "1.2.0"
        }
        dev {
            applicationId "com.example.myproject.dev"
            versionCode 15
            versionName "1.3.6"
        }
    }

    applicationVariants.all { variant ->
        variant.outputs.all { output ->
            def project = "myProject"
            def SEP = "_"
            def flavor = variant.productFlavors[0].name
            def buildType = variant.variantData.variantConfiguration.buildType.name
            def version = variant.versionName
            def date = new Date();
            def formattedDate = date.format('ddMMyy_HHmm')

            def newApkName = project + SEP + flavor + SEP + buildType + SEP + version + SEP + formattedDate + ".apk"

            outputFileName = new File(newApkName)
        }
    }
}