Java Calendar
Java Calendar is a core library in Java's java.util package that provides classes and methods for date and time manipulation, including date arithmetic, formatting, and parsing. It is part of the legacy date-time API in Java, primarily represented by the Calendar abstract class and its concrete implementations like GregorianCalendar. It handles operations such as adding days, comparing dates, and converting between different calendar systems.
Developers should learn Java Calendar when working with legacy Java applications (pre-Java 8) that require date and time handling, as it was the standard API before Java 8's java.time package. It is useful for tasks like scheduling events, calculating durations, or managing dates in older systems, but it has limitations like mutability and complexity. For new projects, it's recommended to use the modern java.time API introduced in Java 8 for better performance and clarity.