Get TimeZone offset value from TimeZone without TimeZone name

Question

I need to save the phone s timezone in the format    - hh mm  I am using TimeZone class to deal with this  but the only format I can get is the following   PST -05 00 GMT  02 00   I would rather not substring the result  is there any key or option flag I can set to only get the value and not the name of that timezone  GMT CET PST

User · Answer

We can easily get the millisecond offset of a TimeZone with only a TimeZone instance and System.currentTimeMillis(). Then we can convert from milliseconds to any time unit of choice using the TimeUnit class.

Like so:

public static int getOffsetHours(TimeZone timeZone) {
    return (int) TimeUnit.MILLISECONDS.toHours(timeZone.getOffset(System.currentTimeMillis()));
}

Or if you prefer the new Java 8 time API

public static ZoneOffset getOffset(TimeZone timeZone) { //for using ZoneOffsett class
    ZoneId zi = timeZone.toZoneId();
    ZoneRules zr = zi.getRules();
    return zr.getOffset(LocalDateTime.now());
}

public static int getOffsetHours(TimeZone timeZone) { //just hour offset
    ZoneOffset zo = getOffset(timeZone);
    TimeUnit.SECONDS.toHours(zo.getTotalSeconds());
}

User · Answer

ZoneId here   ZoneId of  Europe Kiev    ZonedDateTime hereAndNow   Instant now   atZone here   String format   tz   hereAndNow     will give you a standardized string representation like   0300

User · Answer

I know this is old  but I figured I d give my input  I had to do this for a project at work and this was my solution   I have a Building object that includes the Timezone using the TimeZone class and wanted to create zoneId and offset fields in a new class   So what I did was create   private String timeZoneId  private String timeZoneOffset    Then in the constructor I passed in the Building object and set these fields like so   this timeZoneId   building getTimeZone   getID    this timeZoneOffset   building getTimeZone   toZoneId   getId      So timeZoneId might equal something like  EST  And timeZoneOffset might equal something like  -05 00   I would like to not that you might not

User · Answer

I need to save the phone s timezone in the format    - hh mm   No  you don t  Offset on its own is not enough  you need to store the whole time zone name id  For example I live in Oslo where my current offset is  02 00 but in winter  due to dst  it is  01 00  The exact switch between standard and summer time depends on factors you don t want to explore   So instead of storing   02 00  or should it be   01 00   I store  Europe Oslo  in my database  Now I can restore full configuration using   TimeZone tz   TimeZone getTimeZone  Europe Oslo     Want to know what is my time zone offset today   tz getOffset new Date   getTime      1000   60     yields  120 minutes   However the same in December   Calendar christmas   new GregorianCalendar 2012  DECEMBER  25   tz getOffset christmas getTimeInMillis      1000   60     yields  60 minutes   Enough to say  store time zone name or id and every time you want to display a date  check what is the current offset  today  rather than storing fixed value  You can use TimeZone getAvailableIDs   to enumerate all supported timezone IDs

User · Answer

MrBean - I was in a similar situation where I had to call a 3rd-party web service and pass in the Android device s current timezone offset in the format   -hh mm   Here is my solution   public static String getCurrentTimezoneOffset          TimeZone tz   TimeZone getDefault          Calendar cal   GregorianCalendar getInstance tz       int offsetInMillis   tz getOffset cal getTimeInMillis          String offset   String format   02d  02d   Math abs offsetInMillis   3600000   Math abs  offsetInMillis   60000    60        offset    offsetInMillis  gt   0          -     offset       return offset

User · Answer

With java8 now  you can use   Integer offset    ZonedDateTime now   getOffset   getTotalSeconds      to get the current system time offset from UTC  Then you can convert it to any format you want  Found it useful for my case  Example   https   docs oracle com javase tutorial datetime iso timezones html

User · Answer

With Java 8  you can achieve this by following code       TimeZone tz   TimeZone getDefault        String offsetId   tz toZoneId   getRules   getStandardOffset Instant now    getId      and the offsetId will be something like  01 00  Please notice the function getStandardOffset need a Instant as parameter  It is the specific time point  at which you want to check the offset of given timezone  as timezone s offset may varies during time  For the reason of some areas have Daylight Saving Time    I think it is the reason why  Tomasz Nurkiewicz recommand not to store offset in signed hour format directly  but to check the offset each time you need it

[java] Get TimeZone offset value from TimeZone without TimeZone name

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