sqlite convert timestamp to date

Question

how to convert timestamp value 444663422.631236 to date. I tried these ways but does not worked.

public class Teste {
public static void main(String[] args) throws ParseException {
    String l = "480364794";
    String d = "479617200";

    print(convertEpoc("444663422"));

    print(convert("480364794", "dd/MM/yyyy HH:mm:ss"));
    print(convert("479617200", "dd/MM/yyyy HH:mm:ss"));

}

private static String convertEpoc(String d) {
    long epoch = Long.parseLong(d);
    Instant instant = Instant.ofEpochMilli(epoch * 1000);
    ZonedDateTime.ofInstant(instant, ZoneOffset.UTC);
    return instant.toString();
}

public static String convert(String epochSec, String dateFormatStr) {
    Date date = new Date(Long.parseLong(epochSec) * 1000);
    SimpleDateFormat format = new SimpleDateFormat(dateFormatStr,
            Locale.getDefault());
    return format.format(date);
}

public static void print(String s) {
    System.out.println(s);
}}

what am i doing wrong?

`convert` seems to be OK, and what jar did you use in `convertEpoc`? — Blank, May 05 '16 at 02:03
@JoséHolandaNeto What do you mean by “does not worked”? What did you expect and what did you get instead? — Basil Bourque, May 06 '16 at 01:01
@ JoséHolandaNeto Why do you give one kind of example input in the first sentence, but then give entirely different inputs in your example code? Please work to organize your thoughts before posting. — Basil Bourque, May 06 '16 at 01:08

score 0 · Answer 1 · edited May 23 '17 at 12:16

Your Question in inconsistent with two different kinds of input. First we will look at the whole seconds, then we will look at the input with a decimal fraction.

Whole Seconds

No need for multiplying by a thousand when the input is a count of seconds since epoch reference date. The Instant class offers the static method ofEpochSecond to handle whole seconds.

`OffsetDateTime`

When working with only an offset-from-UTC (or UTC itself), use the OffsetDateTime class. The ZonedDateTime class is for assigning a full time zone. A full time zone is an offset-from-UTC plus a set of rules for handling anomalies such as Daylight Saving Time (DST).

So what is the difference between an Instant and an OffsetDateTime assigned UTC as the offset? No difference in the meaning, both represent the same moment. But the OffsetDateTime has additional features. One such feature is flexible formatting when generating a String representation, whereas an Instant is not intended for formatting other than its own toString method.

String input = "480364794";
Instant instant = Instant.ofEpochSecond ( Long.parseLong ( input ) );
OffsetDateTime odt = OffsetDateTime.ofInstant ( instant , ZoneOffset.UTC );

System.out.println ( "input: " + input + " | instant: " + instant + " | odt: " + odt );

When run.

input: 480364794 | instant: 1985-03-22T18:39:54Z | odt: 1985-03-22T18:39:54Z

Fractional Second

For the input of a fractional second, separate the whole number of seconds from the fraction. Then pass each to a static factory method, Instant.ofEpochSecond taking two arguments.

One way of getting those numbers is through BigDecimal. We do not use double/float because those data types trade away accuracy for speed of execution.

See this Question for discussion of extracting fractional part of a BigDecimal. Note especially this Answer and this Answer.

BigDecimal input = new BigDecimal ( "444663422.631236" );

// Seconds
long seconds = input.longValue ();  // = 444,663,422. Truncates the fraction. Only the whole number portion remains.

// Nanoseconds
BigDecimal fractionalSecond = input.remainder ( BigDecimal.ONE );  // = 0.631236. Truncates whole number. Only decimal fraction remains.
int decimalPlacesForNanoseconds = 9;
if ( fractionalSecond.scale () > decimalPlacesForNanoseconds ) {  // Too many decimal places?
    // FIXME: Handle this error condition. This means data loss as our input has a granularity finer than nanoseconds.
    System.out.println ( "ERROR - Input finer than nanoseconds. Message # 0aa71e3b-6a5b-4ac4-b239-68e6b9f12284." );
}
BigInteger nanosBI = fractionalSecond.movePointRight ( decimalPlacesForNanoseconds ).toBigInteger ();  // Make a whole number from the fraction.
long nanos = nanosBI.longValue ();

// Instant = ( Seconds + Nanoseconds )
Instant instant = Instant.ofEpochSecond ( seconds , nanos );

Dump to console.

System.out.println ( "input: " + input + " | seconds: " + seconds + " | nanos: " + nanos + " | instant: " + instant );

When run.

input: 444663422.631236 | seconds: 444663422 | nanos: 631236000 | instant: 1984-02-03T13:37:02.631236Z

sqlite convert timestamp to date

1 Answers1

Whole Seconds

OffsetDateTime

Fractional Second

`OffsetDateTime`