Not able to understand “YYYY-MM-DDTHH:MM:SS” date format

Question

I am trying to parse following date time string

2018-01-30T23:59:59.000

I am not able to understand which standard format it is like UTC or

Answer 1

You need to escape the literal T:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:SS");

See This SO Answer for more examples

Update: Your string is in the format

yyyy-MM-dd'T'HH:mm:ss.SSS

but you are trying to parse it with a completely uppercase format string.

This does not do what you want it to do and you should read the documentation on SimpleDateFormat and the format string placeholders

Answer 2

See the doc of SimpleDateFormat and try this:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");

Answer 3

    LocalDateTime dateTime = LocalDateTime.parse("2018-01-30T23:59:59.000");
    System.out.println(dateTime);

This prints:

2018-01-30T23:59:59

Your string is in ISO 8601 format. UTC or Coordinated Universal Time is not a format, it is a standard time used to define the time the rest of use in our respective time zones.

The date-time classes you were using, SimpleDateFormat and Date, are long outdated and the former in particular notoriously troublesome. I recommend that you instead use java.time, the modern Java date and time API. It is so much nicer to work with.

A LocalDateTime is a date with time of day and without time zone or offset from UTC. Its one-argument parse method parses ISO 8601, which is why no explicit formatter is needed.

What went wrong in your code

Your format pattern string has a number of issues to it. Which is one reason why you should appreciate the above solution without any explicit formatter. The first thing that goes wrong is: Your format pattern string has a colon, :, between seconds and milliseconds, whereas your date-time string has a dot, .. This is why you get the exception.

However, fixing this, your code yields the following Date:

Sun Dec 31 23:00:00 CET 2017

It’s one month off from the expected, and the minutes and seconds are missing. Because:

• Uppercase YYYY is for week-based year and only useful with a week number. You need lowercase yyyy for year.
• Uppercase DD is for day of year. You need lowercase dd for day of month.
• You correctly used uppercase MM for month. Trying the same again for minutes won’t work. Maybe you can guess by now: it’s lowercase mm.
• Not surprising you need lowercase ss for seconds.
• UsingMS for milliseconds is interesting. SimpleDateFormat takes it as M for month (which we’ve already had twice before) and uppercase S for millisecond. Instead you needed uppercase SSS for the three digits of milliseconds.

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Wikipedia article: ISO 8601
• Wikipedia article: Coordinated Universal Time on UTC