How to add hours to unix timestamp or epochmilli in java?

This tutorial explains how to add hours to unix timestamp or epochmilli using TimeUnit in Java. You may face situations like adding hours, minutes and seconds to an timestamp for display purpose in UI. Let’s see how to do that.

Add Hours to Timestamp Example

The below example shows you how to add hours, let’s say 5 hours or today’s current hour to the timestamp.

package com.sneppets.app;

import java.time.LocalDate;
import java.time.ZoneId;
import java.util.concurrent.TimeUnit;

public class TimestampHoursExample {
	
	public static void main (String[] args) {		
		
		LocalDate date  = LocalDate.now();
		ZoneId zoneId = ZoneId.systemDefault();
		long epochTimestamp = date.atStartOfDay(zoneId).toInstant().toEpochMilli();				
		System.out.println("epochTimeStamp : " + epochTimestamp);		
	
		
		int hoursToAdd = 5;
		long hourValue = TimeUnit.HOURS.toMillis(hoursToAdd);
		long finalEpochTimestampWithHoursAdded = epochTimestamp + hourValue;		
		System.out.println("finalEpochTimestampWithHoursAdded : " + finalEpochTimestampWithHoursAdded);
		
	}

Output

epochTimeStamp : 1580754600000
finalEpochTimestampWithHoursAdded : 1580772600000

In the above example we have used LocalDate and converted it to epochmilli and tried to add 5 hours timeunit using java.util.concurrent.TimeUnit util.

Now let us check the results and verify whether hour value is added to the timestamp. To verify this you can use any online epochconverter tool as shown below.

epochTimeStamp

finalEpochTimestampWithHoursAdded

java.util.concurrent.TimeUnit

TimeUnit is an enum and it represents time durations at a given unit of granularity. It supports many units like DAYS, MINUTES, SECONDS etc.,

You need to use timeunit HOURS and toMillis() method of TimeUnit to convert the hours value to milliseconds.

Further Reading

Add Hours to Timestamp Example

java.util.concurrent.TimeUnit

References