Handling dates and times in a computer system is a considerably big challenge. We need to take care of different calendar systems, different time zones, daylight saving switches, and language- and country-dependent date and time formatting.
Java includes a sophisticated date and time handling, which is up to JDK version 7 in the majority of use cases boiled down to using classes java.util.Date, java.util.Calendar, java.text.SimpleDateFormat, and the function System.currentTimeMillis().
Only starting with JDK version ...