Get a LocalDateTime object from a given string?

Question

"2021-09-17 11:48:06 UTC"

I want to parse the following string and create a LocalDateTime object or an Instant

I know you can write something like this

String dateTime = "2021-09-17 11:48:06 UTC";
LocalDateTime dt = LocalDateTime.parse(dateTime,DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

How do I deal with the UTC part in the string?

No. I know how to format strings like how they are doing it in the post you referred me to. I want to know how do I deal with that `UTC` part? — Tendai, Sep 17 '21 at 12:16
"2021-09-17 11:48:06 UTC" isn't a local date time: it's a date time, because it has a time zone. Parse it to a DateTime, then use `toLocalDateTime()`. — Andy Turner, Sep 17 '21 at 12:24
Oh ok, that's different. Thanks you for edit. And yes, such as says by Andy, you have to use global datetime instead of local — Elikill58, Sep 17 '21 at 12:26

Arvind Kumar Avinash · Answer 1 · 2021-09-17T16:53:30.567

Never hardcode the standard timezone text like `UTC`, `GMT` etc.

Never hardcode the standard timezone text like UTC, GMT etc. which DateTimeFormatter is already capable of handling in the best way.

Parse the given Date-Time string using the pattern, uuuu-MM-dd HH:mm:ss VV into a TemporalAccessor from which you can get the Instant as well as the LocalDateTime.

Demo:

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAccessor;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        String strDateTime = "2021-09-17 11:48:06 UTC";

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss VV", Locale.ENGLISH);
        TemporalAccessor temporalAccessor = dtf.parse(strDateTime);

        Instant instant = Instant.from(temporalAccessor);
        LocalDateTime ldt = LocalDateTime.from(temporalAccessor);

        System.out.println(instant);
        System.out.println(ldt);
    }
}

Output:

2021-09-17T11:48:06Z
2021-09-17T11:48:06

ONLINE DEMO

Alternatively:

Parse the given Date-Time string using the pattern, uuuu-MM-dd HH:mm:ss VV into a ZonedDateTime from which you can get the Instant as well as the LocalDateTime.

Demo:

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        String strDateTime = "2021-09-17 11:48:06 UTC";

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss VV", Locale.ENGLISH);

        ZonedDateTime zdt = ZonedDateTime.parse(strDateTime, dtf);
        Instant instant = Instant.from(zdt);
        LocalDateTime ldt = zdt.toLocalDateTime();

        System.out.println(zdt);
        System.out.println(instant);
        System.out.println(ldt);
    }
}

Output:

2021-09-17T11:48:06Z[UTC]
2021-09-17T11:48:06Z
2021-09-17T11:48:06

ONLINE DEMO

Learn more about the modern Date-Time API^* from Trail: Date Time.

^{* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.}

If I ever have a question about a datetime, you are the specialist :-) — The fourth bird, Sep 17 '21 at 15:43
Thanks, @OleV.V. for pointing out the requirement for `Instant`. I have updated the answer to meet that requirement as well. — Arvind Kumar Avinash, Sep 17 '21 at 16:25

Andy Turner · Accepted Answer · 2021-09-17T13:16:30.967

"2021-09-17 11:48:06 UTC" isn't a local date time: it's a date time, because it has a time zone. And because your time has a time zone, it doesn't match your pattern, which doesn't.

If your time strings always end with exactly "UTC", you can make that a literal in the pattern:

DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss 'UTC'");

If you need to handle other time zones than UTC, you can use z:

DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss z");

but note that this is for parsing a zoned date time; from that, you can extract the local date time:

ZonedDateTime zdt = ZonedDateTime.parse(dateTime,DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss z");
LocalDateTime ldt =z dt.toLocalDateTime();

Get a LocalDateTime object from a given string?

2 Answers2

Never hardcode the standard timezone text like UTC, GMT etc.

Alternatively:

Never hardcode the standard timezone text like `UTC`, `GMT` etc.