converting string representation of unknown date-format to Date in java

Question

I have a string that represents a date. I do not know the date format of the string. But for example only, it may be any of

2015-10-14T16:41:42.000Z
2015-10-14T19:01:53.100+01:00
2015-10-14 05:20:29

or any valid format that a website may use to describe date in a meta tag (so the format will be official, as opposed to whimsical, but the set of possibilities is not small).

Can I use joda-time to solve this issue? How about java.util.Date or anything else?

update

I think I find a Javascript equivalent of what I am looking for

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

But I need an answer for Java.

Both of these suggestions require me to know the format beforehand. The very title of my question specifies "unknown" format :). Do you guys know by any chances of a way to get all possible date formats for my circumstance? (Hoping it's a very small set, of course). I don't mind writing multiple parsers, but the thing is the format can be anything that is valid for an html meta tag that contains date. — Katedral Pillon
– Katedral Pillon, Commented Oct 14, 2015 at 20:01
There's no "simple" answer and the general answer is to use a List of formats and keep trying to convert the value against the List of formats until one works — MadProgrammer
– MadProgrammer, Commented Oct 14, 2015 at 20:41
@Gimby your comment is neither intelligent nor helpful nor necessary: the OP provides a link where such a function actually exists for JavaScript. So this is a valuable question. And perhaps Google or Oracle or joda-time or whoever is responsible for creating authoritative Java functions should pay attention. A function like this in Java would be invaluable to many developers. — Konsol Labapen
– Konsol Labapen, Commented Oct 14, 2015 at 21:19
@KatedralPillon yours (assuming always a 24-hour clock) look like 4-digit-year, literal_dash, 2-digit-month, literal_dash, 2-digit-day, one-space-or-literal_T, 2-digit-hour, literal_colon, 2-digit-minute, literal_colon, 2-digit-second (etc). A regex (w/o checking valid ranges) is like \d{4}-\d{2}-\d{2}[ T]\d{2}:\d{2}:\d{2}(\.\d{3})?(.*)? (add proper capturing groups to extract pieces) the (\.\d{3})? is optional 3-digit hundredths of a second; the final (.*)? is the optional time-zone info, which needs more parsing to tell if its a zone (Z, EST, etc.) or an offset (+01:00) — Stephen P
– Stephen P, Commented Oct 15, 2015 at 22:12

max · Accepted Answer · 2015-10-14 21:48:48Z

1

well this is not a real "java" solution, but if you have found a Javascript one, than you can use the Javascript solution in java using the ScriptEngine.

just a little quick and dirty... :)

here is a sample code:

public static void main(String[] args) throws ScriptException, ParseException {
    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("js");
    String[] dateStrings = new String[] {
            "2015-10-14T16:41:42.000Z",
            "2015-10-14T19:01:53.100+01:00",
            "2015-10-14 05:20:29" };

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
    for (String d : dateStrings) {
        String script = "new Date('" + d + "')";
        Object eval = engine.eval(script);
        Date parsed = sdf.parse(eval.toString().replace("[Date ", "").replace("]", ""));
        System.out.println(eval + " -> " + parsed);

    }

}

that prints out:

[Date 2015-10-14T16:41:42.000Z] -> Wed Oct 14 18:41:42 CEST 2015
[Date 2015-10-14T18:01:53.100Z] -> Wed Oct 14 20:01:53 CEST 2015
[Date 2015-10-14T03:20:29.000Z] -> Wed Oct 14 05:20:29 CEST 2015

The eval.toString() part can be improved obviously. as the locale settings...

edited Oct 14, 2015 at 21:48

answered Oct 14, 2015 at 21:24

max

8038 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Katedral Pillon Over a year ago

I am looking at the page, but I am not really sure what I am looking at. Do you mind showing a short code of how I would call the JS new Date(dateString) construction in Java using the ScriptEngine?

Katedral Pillon Over a year ago

I don't know if your example works, but the ScriptEngine idea should, so I am testing some code (yours and my own versions) and will report back once I am successful. In the meantime +1.

Katedral Pillon Over a year ago

shouldn't the following work? String script = "var date = new Date('" + dateString + "'); var timestamp = date.getTime();"; and then long timestamp = ((Long) engine.get("timestamp")).longValue(); ?

max Over a year ago

yes it works but you have to eval the script string engine.eval(script); and then get the var but casting to Double and not to Long: long timestamp = ((Double) engine.get("timestamp")).longValue();

Katedral Pillon Over a year ago

The answer may not be native Java, but until Joda-time gives use a better answer, this is it. I use the code snippet I show you, with the Double correction.

Collectives™ on Stack Overflow

converting string representation of unknown date-format to Date in java

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related