How System.currentTimeMillis()/1000 working in JAVA

Question

I just want to understand the currentTimeMillis()/1000L method in System class. As per my understanding that this method will return current time in seconds. I have a doubt here If I run the same code in Local jvm (IST) , and remote box(Sanjose) will return different values as output?

Can someone explain me how does it work if we run the code in different JVM which is USA and India what will be the output. Does it return same output? or different?

It uses UTC no matter what time zone you are in. So, yes it will be the same anywhere in the world. See also: https://stackoverflow.com/q/17271039/669576 — 001, Aug 27 '18 at 18:55
Something important most people left out was the fact that none of this will matter if both computers haven’t synced with an NTP recently. — vandench, Aug 27 '18 at 22:07
If you want seconds rather than milliseconds, I would prefer `Instant.now().getEpochSecond()`. It’s clearer to read that doing your own division by 1000. Making your own time conversions is a poor habit. — Ole V.V., Aug 28 '18 at 06:03

score 4 · Accepted Answer · answered Aug 27 '18 at 18:45

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It returns number of ms since the beginning of unix epoch, which is time-zone independent. Therefore, it should return the same output.

answered Aug 27 '18 at 18:45

irahavoi

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It won't differ? if we run the code in different JVM? like different countries. Will it give same output? – ArrchanaMohan Aug 27 '18 at 18:49
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If you simultaneously run the code in 2 different JVMs located in different countries (but having the same implementation) result should be the same. Because, no matter where you're located, the number of milliseconds passed since beginning of Unix Epoch will be the same. – irahavoi Aug 27 '18 at 18:57
Thank you. It really helps. – ArrchanaMohan Aug 27 '18 at 19:02
Accept your answer. – ArrchanaMohan Aug 27 '18 at 19:02
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It will differ if one of the device clocks has been set incorrectly since it uses the system clock. Other than that it won’t. – Ole V.V. Aug 28 '18 at 05:59

score 3 · Answer 2 · answered Aug 27 '18 at 18:47

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The code will return the same output because .currentTimeMillis() function uses the UTC timezone rather than a local timezone of the JVM.

See Oracle's documentation: https://docs.oracle.com/javase/7/docs/api/java/lang/System.html#currentTimeMillis()

answered Aug 27 '18 at 18:47

Hayes Roach

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score 0 · Answer 3 · answered Aug 27 '18 at 18:44

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it gives the amount of milliseconds that have passed since Epoch time which is 00:00:00 on 1 January 1970. It is also called Unix time. Learn more about it here https://en.wikipedia.org/wiki/Unix_time

answered Aug 27 '18 at 18:44

Maurice

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How System.currentTimeMillis()/1000 working in JAVA

3 Answers3