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I'm a bit baffled what format these timestamps are in. I was told the format to use is yyyy-MM-dd.HH:mm:ss but all of the timestamps appear like this 2017-01-01 00:08:57.231, 2017-01-01 07:43:36.348, or 2017-01-01 13:25:55.683. I'm not understanding why there are four sections to the time ?:Hour:Minute:Second in the actual data I have when the format I'm supposed to be using only has three time sections. Are these datetime timestamps not actually in the format of yyyy-MM-dd.HH:mm:ss?

Kyle Bridenstine
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  • I'm not sure I understand what is your question... – Liora Haydont Apr 05 '18 at 19:11
  • Well, there is no dot between the date and the time, and there are milliseconds after the seconds. So how coult it match the format `yyyy-MM-dd.HH:mm:ss`, which *has* a dot between date and time, and which *doesn't* have milliseconds after the seconds? – JB Nizet Apr 05 '18 at 19:11
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    `2017-01-01 13:25:55.683` and `2017-01-01 00:08:57.231` are in the format `yyyy-MM-dd.HH:mm:ss.SSS` the trailing 3 `S`s are fractional seconds – xtratic Apr 05 '18 at 19:11
  • @xtratic I still can't seem to parse the strings 2017-01-01 13:25:55.683 to a date using the format yyyy-MM-dd.HH:mm:ss.SSS. – Kyle Bridenstine Apr 05 '18 at 19:17
  • @xtratic SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd.HH:mm:ss:SSS"); formatter.parse("2017-01-01 13:25:55.683"); throws Unparseable date: "2017-01-01 13:25:55.683" – Kyle Bridenstine Apr 05 '18 at 19:17
  • @Mr.Tea sorry, my format was botched in the first comment, since I just copied and used yours as a template. The right format is `yyyy-MM-dd HH:mm:ss.SSS` . But please learn to read the Javadoc as @JB Nizet says, all this information is right there. – xtratic Apr 05 '18 at 19:20
  • @Mr.Tea pay attention. Again, you have a dot in your pattern between the date and the time, but there is no dot in the input. And the milliseconds are separated by a dot in the input, not by a colon as in your pattern. You seem to be trying random things instead of reading the comments you got and the javadoc and applying common sense. – JB Nizet Apr 05 '18 at 19:21
  • @JB Nizet please comment above this one. – Kyle Bridenstine Apr 05 '18 at 19:23
  • @Mr.Tea The issue was that you originally posted `yyyy-MM-dd.HH:mm:ss` we didn't notice the `.` rather than ` ` (space) in the middle and just added the `.SSS` part. – xtratic Apr 05 '18 at 19:25
  • @xtratic I see that I'm just saying the people I got this data from explicitly said it was in the format yyyy-MM-dd.HH:mm:ss and it's not. – Kyle Bridenstine Apr 05 '18 at 19:26
  • Ah, gotcha. Yep, that happens quite a bit actually. Lies about formats and broken standards all over. – xtratic Apr 05 '18 at 19:28
  • @Mr.Tea I recommend you avoid the `SimpleDateFormat` class. It is not only long outdated, it is also notoriously troublesome. Today we have so much better in [`java.time`, the modern Java date and time API](https://docs.oracle.com/javase/tutorial/datetime/). – Ole V.V. Apr 05 '18 at 20:06

2 Answers2

1

No, your suspicion is correct, your example date-time strings are not in the format yyyy-MM-dd.HH:mm:ss. The dot between dd and HH must be a simple mistake, it should be a space since there is a space between date and time in the timestamp strings. Furthermore all of your example strings include milliseconds: in 00:08:57.231 you’ve got 57 seconds and 231 milliseconds, or if you like, 57.231 seconds, so the last section may also be referred to as fraction of second.

    DateTimeFormatter formatter
            = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSS");
    String timestampString = "2017-01-01 00:08:57.231";
    LocalDateTime dateTime = LocalDateTime.parse(timestampString, formatter);
    System.out.println(dateTime);

Output:

2017-01-01T00:08:57.231

For the nerdily curious: It is possible to parse the string, or more precisely most of it, with the format you had been given, only correcting the dot into a space:

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    String timestampString = "2017-01-01 00:08:57.231";
    LocalDateTime dateTime = LocalDateTime.from(
            formatter.parse(timestampString, new ParsePosition(0)));

In this case the result comes without the milliseconds:

2017-01-01T00:08:57

I see no reason why you should want this, though.

Avoid SimpleDateFormat

In a comment you gave a snippet that uses the SimpleDateFormat class. This class is not only long outdated, it is also notoriously troublesome. I see no reason why you should want to use it. Instead I am using java.time, the modern Java date and time API. In my experience it is so much nicer to work with.

Links

Oracle tutorial: Date Time explaining how to use java.time. You may especially want to study the section Parsing and Formatting.

Ole V.V.
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These time stamps are in yyyy-MM-dd HH:mm:ss:ms format, last three digits are milliseconds.

Ole V.V.
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Yuvaraj Chitela
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  • Why the downvote? This answer may be short and not very well explained, but it’s at least to the point and perfectly correct. – Ole V.V. Apr 05 '18 at 19:40