How to adjust a Timestamp that comes from my database?

user_10322015 0
Viewed 105

In the database, a time is saved as a Timestamp in the UTC time zone (that is, 0). When I get it, I need to add the Timezone from the place that I will send. I have these two pieces of information, but I can't find the time.

This is the code from which I get both information. I've tried to transform to LocalDateTime and adjust the zone, but it didn't produce any results. There is no much of code:

Timestamp timestamp = resultQueryCamerasOffline.getLastOnline();
String zoneId = resultQueryCamerasOffline.getEmpresaTimezone();
System.out.println(timestamp.toString());
System.out.println(zoneId);

2020-03-12 03:01:45.0

America/São_Paulo

In the database, last_online has value:

2020-03-12 03:01:45.0
date java
2 Answers

You can and maybe have to use a LocalDateTime in order to achieve what you want, but the final product should be a ZonedDateTime.

Basically, the timestamp should be converted to a LocalDateTime and that LocalDateTime can then be converted to a ZonedDateTime by adding a specific ZoneId, like this:

Just adding a zone, leaving the datetime as is:

public static void main(String[] args) {
    // get or take a timestamp
    java.sql.Timestamp timestamp = Timestamp.valueOf("2020-03-12 03:01:45.0");
    // transforming it into a LocalDateTime
    LocalDateTime localDateTime = timestamp.toLocalDateTime();
    // now create a ZonedDateTime by putting a zone
    ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime,
                                                    ZoneId.of("America/Sao_Paulo"));
    // and print the result
    System.out.println(zonedDateTime);
}

The output is

2020-03-12T03:01:45-03:00[America/Sao_Paulo]

If you are sure the client that runs this code always has the desired time zone, then you can alternatively use ZoneId.systemDefault() when the ZonedDateTime is being created.

But if you don't just want to add a zone but really convert the Instant to another zone, then you can do this:

Converting the Instant to another time zone:

public static void main(String[] args) {
    // get or take a timestamp
    java.sql.Timestamp timestamp = Timestamp.valueOf("2020-03-12 03:01:45.0");
    // transforming it into a LocalDateTime
    LocalDateTime localDateTime = timestamp.toLocalDateTime();
    // now create a ZonedDateTime by putting a zone
    ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(
            localDateTime.toInstant(ZoneOffset.of("+00:00")),
            ZoneId.of("America/Sao_Paulo"));
    // and print the result
    System.out.println(zonedDateTime);
}

This outputs

2020-03-12T00:01:45-03:00[America/Sao_Paulo]

You can have the second one shorter:

public static void main(String[] args) {
    // get or take a timestamp
    java.sql.Timestamp timestamp = Timestamp.valueOf("2020-03-12 03:01:45.0");
    // transforming it into a LocalDateTime
    ZonedDateTime utc = ZonedDateTime.of(timestamp.toLocalDateTime(), ZoneId.of("UTC"));
    // now create a ZonedDateTime by putting a zone
    ZonedDateTime saoPaulo = utc.withZoneSameInstant(ZoneId.of("America/Sao_Paulo"));
    // and print the result
    System.out.println(saoPaulo);
}

The output stays

2020-03-12T00:01:45-03:00[America/Sao_Paulo]

If you want the output formatted differently, you have to either choose one of the built-in patterns (public constants of DateTimeFormatter, like DateTimeFormatter.ISO_ZONED_DATE_TIME) or give it a custom one (by DateTimeFormatter.ofPattern(String pattern) plus an optional Locale):

public static void main(String[] args) {
    // get or take a timestamp
    java.sql.Timestamp timestamp = Timestamp.valueOf("2020-03-12 03:01:45.0");
    // transforming it into a LocalDateTime
    ZonedDateTime utc = ZonedDateTime.of(timestamp.toLocalDateTime(), ZoneId.of("UTC"));
    // now create a ZonedDateTime by putting a zone
    ZonedDateTime saoPaulo = utc.withZoneSameInstant(ZoneId.of("America/Sao_Paulo"));
    // create a formatter for your locale and with the desired pattern
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEEE dd MMM yyyy hh:mm:ss a xxx",
            Locale.forLanguageTag("pt-BR"));
    // and print the result
    System.out.println(saoPaulo.format(dtf));
}

This time, the output is formatted in a totally different way:

Quinta-feira 12 mar 2020 12:01:45 AM -03:00
user_17121350

get the millis from your timestamp and try:

LocalDateTime date = LocalDateTime
.ofInstant(Instant.ofEpochMilli(timestamp.getTime()), ZoneId.systemDefault(yourTimezone()));

or try using a ZonedDateTime

user_61571940
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