How to write build time stamp into apk

Question

1. Making some changes in Android Contacts package
2. Using mm (make) command to build this application

Because I have to change and

Answer 1

For time stamping and versioning, build.gradle/android/defaultConfig:

def buildDateStamp = new Date().format("yyyyMMdd").toInteger()
versionCode buildDateStamp
versionName "$buildDateStamp"
buildConfigField "String", "BUILD_DATE_STAMP", "\"$buildDateStamp\""

Usage in code: BuildConfig.BUILD_DATE_STAMP

resValue "string", "build_date_stamp", "$buildDateStamp"

Usage in xml: "@string/build_date_stamp"

Caveat: adding HHmm will cause errors (probably integer overflow)