Joda DateTime to Unix DateTime

Question

It's odd enough, but I didn't find any result about converting Joda(Time) DateTime to Unix DateTime (or timestamp, whichever is the correct name). How can I do this?

Answer 1

Any object that inherits from BaseDateTime (including DateTime) has the method

public long getMillis()

According to the API it:

Gets the milliseconds of the datetime instant from the Java epoch of 1970-01-01T00:00:00Z.

So a working example to get the seconds would simply be:

new DateTime().getMillis() / 1000

For completeness, the definition of the Unix Timestamp according to Wikipedia:

Unix time, or POSIX time, is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, not counting leap seconds.

You can also improve it further by removing the magic number division using the TimeUnit API:

import java.util.concurrent.TimeUnit;

TimeUnit.MILLISECONDS.toSeconds(new DateTime().getMillis());

Answer 2

Java 8 added a new API for working with dates and times. With Java 8 you can use

long unixTimestamp = Instant.now().getEpochSecond();

Answer 3

    @Test
    public void covertDateTimeToEpoch() {
        DateTime dateTime = DateTime.parse("2020-07-09T04:30:45.781Z");
        long epochMilli = dateTime.toDate().toInstant().toEpochMilli();
        assertEquals(1594269045781L, epochMilli);
    }