CODEWITHSUNDEEP
javadatetimezone
kumar Anny
kumar Anny

Reputation: 366

Get timeZone information from date with date with offset value

we have the below date having offset -07, which belong to "US/Pacific" time zone.

String startTime = "2020-06-12T09:30:00.000-07:00";

I want to retrieve timezone info ("US/Pacific") from above date object.

Upvotes: 2

Views: 537

Answers (2)

deHaar
deHaar

Reputation: 18588

You can parse the String to an OffsetDateTime (knows offset only), extract the ZoneOffset from it, use it to compare a ZonedDateTime (knows zone and offset) for every available ZoneId with this offset and store the ones with equal offsets.

The following method gives you a list of possible ZoneIds for an OffsetDateTime parsed from the String you have:

private static SortedSet<String> getAllZoneIdsFor(OffsetDateTime offsetDateTime) {
    // initialize a data structure for the result
    SortedSet<String> result = new TreeSet<>();
    // extract the zone offset from the given OffsetDateTime
    ZoneOffset zoneOffset = offsetDateTime.getOffset();

    // then check all available zone ids for a matching offset
    for (String zone : ZoneId.getAvailableZoneIds()) {
        // create a ZoneId object from the string
        ZoneId zoneId = ZoneId.of(zone);
        // create a ZonedDateTime from the given LocalDateTime adding the zone
        ZonedDateTime zonedDateTime = offsetDateTime.atZoneSameInstant(zoneId);
        // and check if the extracted offset equals the one of the current zone
        if (zonedDateTime.getOffset().equals(zoneOffset)) {
            // and add the zone id to the result if it does
            result.add(zoneId.toString());
        }
    }

    return result;
}

You would use it in a main() like this

public static void main(String[] args) {
    // take the offset dateime string
    String bookingStartTime = "2020-06-12T09:30:00.000-07:00";
    // parse it to an OffsetDateTime
    OffsetDateTime offsetDateTime = OffsetDateTime.parse(bookingStartTime);

    // get the zones with the offset of the given OffsetDateTime
    SortedSet<String> matchingZones = getAllZoneIdsFor(offsetDateTime);
    // and print them all
    matchingZones.forEach(System.out::println);
}

and see the output

America/Creston
America/Dawson
America/Dawson_Creek
America/Ensenada
America/Fort_Nelson
America/Hermosillo
America/Los_Angeles
America/Phoenix
America/Santa_Isabel
America/Tijuana
America/Vancouver
America/Whitehorse
Canada/Pacific
Canada/Yukon
Etc/GMT+7
Mexico/BajaNorte
PST8PDT
SystemV/MST7
SystemV/PST8PDT
US/Arizona
US/Pacific
US/Pacific-New

Please note you won't be able to find a particular ZoneId just providing an offset. You would need more information (e.g. the system locale) in order to determine a specific zone for a given offset.

Upvotes: 2

assylias
assylias

Reputation: 328913

You can get a list of zones that have a -7h offset at that particular moment in time, but it will not be unique. For example you could use this code:

String bookingStartTime = "2020-06-12T09:30:00.000-07:00";
OffsetDateTime odt = OffsetDateTime.parse(bookingStartTime);
Set<String> allZones = new HashSet<>();
for (String z : ZoneId.getAvailableZoneIds()) {
  ZoneId id = ZoneId.of(z);
  ZonedDateTime zdt = odt.atZoneSameInstant(id);
  if (zdt.getOffset().equals(odt.getOffset())) allZones.add(z);
}

for (String z : allZones) System.out.println(z);

And the output is:

US/Pacific-New
America/Tijuana
SystemV/PST8PDT
US/Arizona
America/Santa_Isabel
Canada/Yukon
Canada/Pacific
America/Creston
America/Phoenix
America/Dawson_Creek
America/Los_Angeles
America/Whitehorse
America/Ensenada
America/Dawson
PST8PDT
America/Hermosillo
America/Vancouver
SystemV/MST7
Etc/GMT+7
America/Fort_Nelson
US/Pacific
Mexico/BajaNorte

Upvotes: 4

Related Questions