What is the difference between android.text.format.DateFormat and java.text.DateFormat

I read some posts on formatting date on android, like this: How do you format date and time in Android? People suggest use `android.text.format.DateFormat` rather than `java.text.DateFormat`, Also here, it mention a problem when converting date to string in android: Android load timezone too long: Loaded time zone names for en_US I am wondering what's the difference between `android.text.format.DateFormat` and `java.text.DateFormat`?