Question

The following code cannot pass the assertion under the Android emulator:

TimeZone timezone = TimeZone.getTimeZone("Hongkong");
Locale locale = new Locale("zh", "HK"); 
Calendar calendar = Calendar.getInstance(timezone, locale);

calendar.set(Calendar.YEAR, 1979);
calendar.set(Calendar.MONTH, 4);        
calendar.set(Calendar.DAY_OF_MONTH, 13);            
calendar.set(Calendar.HOUR_OF_DAY, 4);  
calendar.set(Calendar.MINUTE, 30);      
calendar.set(Calendar.SECOND, 0);        

DateFormat df = DateFormat.getDateTimeInstance(DateFormat.LONG, DateFormat.LONG, locale);
df.setTimeZone(timezone);
String sDate = df.format(calendar.getTime());

int debug = calendar.get(Calendar.HOUR_OF_DAY);
Assert.assertEquals("Error datetime: " + sDate, 4, debug);

And I found that, if change the DAY_OF_MONTH to 12, the error is gone:
calendar.set(Calendar.DAY_OF_MONTH, 12);

Note that this problem is not exists on JUnit test. (without Android)

Finally, this problem seems may not be exists on Android real machine.

Any comments?

Answer 1

I believe, it’s because of this transition:

Hong Kong adopted daylight saving measures in 1941. However, in the 1970s, the government found these measures unnecessary as Hong Kong is at a relatively low latitude. The practice was eliminated in 1979.

Here is the DST change which happened on 13th May 1979.

Sunday, May 13, 1979 3:29:59 AM No UTC+8h HKT

3:30:00 AM → 4:30:00 AM +1h UTC+9h HKST DST starts

Sunday, October 21, 1979 3:29:59 AM +1h UTC+9h HKST

Since DST for Hong Kong went ON and OFF and finally OFF, it may be the root cause of the issue.