How to get the current date and timezone in numeric format

Just complementing @ Ole VV's answer , I found another way to do it using ThreeTenABP , but without replacing the regex (although I don't think it is much easier, more on that below).

Using DateTimeFormatterBuilder

, you can use HashMap

which maps the offset values ​​to String

. That way, for whole hours of offset (for example +03:00

), you can map the corresponding value to a string +3

, etc.

The only problem is that it ZoneOffset

has seconds precision . Both the minimum and maximum values ​​are equal to UTC-18:00:00

and respectively UTC+18:00:00

. Thus, all the possible values of UTC-18:00:00

, UTC-17:59:59

, UTC-17:59:58

and so on. And the formatting requires all possible values ​​to be displayed (otherwise it will display the offset seconds value), so the map will have over 120k entries!

To build this map, I did 2 loops:

• The first cycle displays all hour offsets ( +01:00
  
  before +1
  
  , -02:00
  
  before -2
  
  , etc.)
• The second loop displays all other values ​​(they remain unchanged):
  • whole hours> = 10 (for example +10:00
    
    )
  • not whole hours (for example +05:30
    
    )

Code to create formatting:

// builds a hashmap to map all offset values
Map<Long, String> map = new HashMap<>();

// First loop: Map whole hours from 1 to 9 and from -9 to -1
// So a "+01:00" offset is displayed as "+1"
for (int i = 1; i <= 9; i++) {
    long seconds = ZoneOffset.ofHours(i).getTotalSeconds();
    // 1 hour offset maps to "+1" and so on
    map.put(seconds, "+" + i);
    // -1 hour offset maps to "-1" and so on
    map.put(-seconds, "-" + i);
}

// second loop: Need to map all other possible values for not-whole hours
// offsets like "+10:00" and "+01:30" are not changed
int minOffset = ZoneOffset.MIN.getTotalSeconds();
int maxOffset = ZoneOffset.MAX.getTotalSeconds();
for (long i = minOffset; i <= maxOffset; i++) {
    // the map already contains whole hours, don't need to overwrite the values
    if (!map.containsKey(i)) {
        // uses default String representation (like "+05:30")
        map.put(i, ZoneOffset.ofTotalSeconds((int) i).getId());
    }
}

// create the formatter
DateTimeFormatter formatter = new DateTimeFormatterBuilder()
                // year/month/day and the "|"
                .appendPattern("uuuu/MM/dd | ")
                // use the map of custom values (offset will use the values in the map)
                .appendText(ChronoField.OFFSET_SECONDS, map)
                // create formatter
                .toFormatter();

      

        
        
        
      

    

Some tests:

LocalDateTime dt = LocalDateTime.of(2017, 5, 1, 10, 0);
ZonedDateTime z = ZonedDateTime.of(dt, ZoneId.of("America/Sao_Paulo")); // UTC-03:00
System.out.println(formatter.format(z)); // 2017/05/01 | -3

// just picking some timezone in Arabia Stardard Time
// (there are more than one timezone in AST: https://en.wikipedia.org/wiki/UTC%2B03:00#Arabia_Standard_Time)
// I don't know in which one you are
z = ZonedDateTime.of(dt, ZoneId.of("Asia/Qatar")); // UTC+03:00
System.out.println(formatter.format(z)); // 2017/05/01 | +3

// 2-digit offset
z = ZonedDateTime.of(dt, ZoneId.of("Asia/Vladivostok")); // UTC+10:00
System.out.println(formatter.format(z)); // 2017/05/01 | +10:00

// not whole hour
z = ZonedDateTime.of(dt, ZoneId.of("Asia/Kathmandu")); // UTC+05:45
System.out.println(formatter.format(z)); // 2017/05/01 | +05:45

      

        
        
        
      

    

Output:

2017/05/01 | -3
2017/05/01 | +3
2017/05/01 | +10: 00
2017/05/01 | +05: 45

Notes:

• I don't know if it's better to have a map with 120K maps than using regular expressions (that's up to you). This approach creates a large map, but at least does not require post-processing of the output afterwards (not sure if this is a reasonable compromise)
• If you want shifts for an entire hour> = 10 to display as +10
  
  , +11
  
  etc., just change the first loop for
  
  to for (int i = 1; i <= maxOffsetYouWant; i++)
  
  - just reminding you that the maximum possible value for maxOffsetYouWant
  
  is 18 .