Java - Convert Unix epoch time to date

Question

I need to convert some epoch time stamps to the real date and have used some of the methods I found on stack overflow, but they give the wrong answer.

As an example, one date is "129732384262470907" in epoch time, which is "Mon, 20 Jan 6081 05:24:22 GMT" using http://www.epochconverter.com/

However, my code generates: "Wed Dec 24 14:54:05 CST 19179225"

  String epochString = token.substring(0, comma);
  long epoch = Long.parseLong(epochString);
  Date logdate = new Date(epoch * 1000);
  BufferedWriter timewrite = new BufferedWriter(new FileWriter(tempfile, true));
  timewrite.write(logdate);
  timewrite.flush();
  timewrite.close();

The initial timestamp is in miliseconds, which in the examples I saw here I am supposed to multiply by 1000.

If I don't multiply by 1000, I get: "Mon Aug 08 01:14:30 CDT 4113025"

Both of which are wrong.

So where have I made my error?

Jon Skeet · Accepted Answer · 2012-03-10 17:49:37Z

2

129732384262470907 is actually in microseconds since the epoch if it's meant to be 6081, so you need to divide by 1000 if that's real input.

Note that epochconverter.com doesn't even handle that value - it only allows you to enter 129732384262470 which it then treats as milliseconds since the epoch.

You need to multiply by 1000 if your data is seconds since the epoch. Basically all you need to know is that Java expects milliseconds since the epoch; the rest should be plain sailing, assuming you know what your input data actually means.

If you could provide your real data, and what it's meant to represent, it's probably going to be easy to fix your problems.

edited Mar 10, 2012 at 17:49

answered Mar 10, 2012 at 17:43

Jon Skeet

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1 Comment

Sore Finger Tips Over a year ago

Thanks for the tip about epochconveter.com I would have never figured that out on my own. And as you can see from my post below, between your two answers, I was able to figure it out.

dty · Accepted Answer · 2012-03-10 17:43:56Z

0

If you look carefully, epochconverter.com truncated that number because it was too long for the entry field.

I suggest you print the current value of System.currentMillis() to see what approximate range a "current" epoch-based timestamp has, and re-scale your input number to match. I think you'll probably have to divide by 1000.

In fact, looking closer, if you divide by 10,000, you get 1297323842624, which comes out to a date in 2011. So it's not at all clear what units the number you've given are in.

answered Mar 10, 2012 at 17:43

dty

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3 Comments

Sore Finger Tips Over a year ago

And you're awesome!! That one change made it work properly. Thanks again, and you're correct the epochconverter.com was giving an incorrect value the real time is "Sun Jan 19 23:24:22 CST 6081"

dty Over a year ago

Really? You're expecting the year 6081?

Sore Finger Tips Over a year ago

Of course, I'm a time traveler. I just need to get back to 6081 and the primitive systems available are very frustrating. [/joke] Sorry, pasted the wrong one, the correct one is this: "Thu Feb 10 01:44:02 CST 2011" I had to divide by 100,000

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