What is Epoch time and how do you get it in Java?

  • Epoch time, also known as Unix time or POSIX time, is a system for representing timestamps as the number of seconds that have elapsed since a specific reference point called the “epoch.”
  • The epoch is a fixed point in time from which all other timestamps are measured.
  • In the context of Unix-based operating systems and programming, the epoch time is defined as the number of seconds that have passed since January 1, 1970, at 00:00:00 Coordinated Universal Time (UTC). This moment is commonly referred to as the “Unix Epoch” or “Unix Time.”
  • The use of epoch time has several advantages, including:
    • Simplicity: Representing time as a single integer (number of seconds) simplifies date and time calculations in programming.
    • Portability: Epoch time is not dependent on any time zone, making it easy to store and transmit timestamps across different systems and locations.
    • Precision: Using seconds as the unit of measurement provides sufficient precision for many applications.
  • To convert a specific timestamp into epoch time, you can calculate the number of seconds that have passed between that timestamp and the Unix Epoch. Conversely, to convert an epoch time back to a human-readable date and time, you can add the epoch time to the Unix Epoch reference point.
  • Code to get epoch time and covert it to Local date and time in Java
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;

public class EpochTime {

    public static void main(String[] args) {

        //Get epoch time
        long epochSeconds = Instant.now().toEpochMilli();
        System.out.println("Epoch in Milliseconds: " + epochSeconds);

        // Convert epoch time to Java LocalDateTime
        Instant instant = Instant.ofEpochMilli(epochSeconds);
        LocalDateTime dateTime = instant.atZone(ZoneId.systemDefault()).toLocalDateTime();

        System.out.println("Java LocalDateTime: " + dateTime);


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