How to round off timestamp in milliseconds to nearest seconds?

Question

How to round off the current timestamp in milliseconds to seconds?

If this is the current timestamp in milliseconds I have -

1384393612958

The if I am rounding off to nearest second then will it be like this?

Time in MS rounded off to nearest Second = 1384393612000

I might need to do this both in Java and C++.

score 9 · Accepted Answer · answered Dec 04 '13 at 20:25

9

If you are using Python:

old_number = 1384393612958
new_number = 1000 * (old_number / 1000)

print new_number

Basically you want to use an integer number, divide by one thousand (to shave off the milli-seconds), and then multiple by thousand to get the ms value rounded to seconds.

answered Dec 04 '13 at 20:25

Suman

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Technically, that's truncating the number to the previous second, not rounding to nearest, which would be more like `1000 * ((old_number + 500) / 1000)`... – twalberg Dec 04 '13 at 20:32
1

@twalberg, While true, TrekkieTechie's example truncates the number. – Brian S Dec 04 '13 at 21:31
@BrianS Hmmm... I hadn't noticed that, but you're right... So it seems OP isn't sure whether they want rounding or truncation. – twalberg Dec 04 '13 at 22:06
In Python you can obtain it rounded from the beginning: int(round(time.time())) – Sandman Dec 14 '13 at 07:01
1

For Python 3, replace `/` with `//` – Anton3 Oct 19 '20 at 15:16

score 4 · Answer 2 · answered Dec 05 '13 at 15:05

4

In Java you can use Calendar to something like this:

Calendar cal = Calendar.getInstance().setTimeInMillis(millisec);
int seconds = cal.get(Calendar.SECONDS);

Alternatively (and can work for C++ too) you can do:

int sec = ((millisec + 500) / 1000);

adding 500 ms allows you to round the number properly.

answered Dec 05 '13 at 15:05

Luca S.

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FYI, this code uses troublesome old date-time classes that are now legacy, supplanted by the java.time classes. – Basil Bourque Nov 15 '17 at 10:38

score 2 · Answer 3 · edited Jun 20 '20 at 09:12

tl;dr

Instant.ofEpochMilli( 1_384_393_612_958L ) 
       .truncatedTo( ChronoUnit.SECONDS )
       .toEpochMilli()

java.time

The modern approach in Java uses the java.time classes.

The Instant class represents a point on the timeline in UTC with a resolution of nanoseconds.

Instant instant = Instant.ofEpochMilli( 1_384_393_612_958L ) ;
Instant instantTrunc = instant.truncatedTo( ChronoUnit.SECONDS ) ;
long millis = instantTrunc.toEpochMilli() ;

score 0 · Answer 4 · answered Nov 15 '17 at 08:19

This is needed to convert java date object to mysql datetime formatted string in sql queries.

Conversion:

Calendar cal = Calendar.getInstance();
cal.setTime(this.id.getCreatedOn());
if (cal.get(Calendar.MILLISECOND) >= 500 ) {
  System.out.println("Round off milliseconds to seconds");
  cal.set(Calendar.SECOND, cal.get(Calendar.SECOND) + 1);
}
Date roundedCreatedOn = cal.getTime();

Actual query string contains:

createdOn = '" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(roundedCreatedOn)+ "'"

without this, mysql's timestamp column did not match the query generated using new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(roundedCreatedOn) as SimpleDateFormat just drops additional milliseconds. — AravindR, Nov 15 '17 at 08:20

score 0 · Answer 5 · answered Jan 12 '19 at 20:54

0

In javascript, using the moment.js library:

moment(timestamp).startOf('second')

answered Jan 12 '19 at 20:54

James Gentes

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How to round off timestamp in milliseconds to nearest seconds?

5 Answers5

tl;dr

java.time