[WICKET-6689] ClientProperties.getTimeZone() has some issue when DST and UTC offsets are different

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 9.0.0-M2
• Fix Version/s: 8.6.1, 7.15.0, 9.0.0-M3
• Component/s: wicket
• Assignee: Martin Tzvetanov Grigorov
• Reporter: Mansour Rahimi
• Created: 17/Jul/19 23:53
• Updated: 23/Jul/19 11:04
• Resolved: 22/Jul/19 13:13

Description

So ClientProperties.getTimeZone() got UTC offset 11 and DST offset 10 (Australia Sydney), and it picked the wrong one (UTC +11). The issue is the way it's calculating the UTC-DST difference and looking up in the available time zone IDs.

					if (dstTimeZone != null &&
						dstTimeZone.getRawOffset() != timeZone.getRawOffset())
					{
						int dstSaving = dstTimeZone.getRawOffset() - timeZone.getRawOffset();
						String[] availableIDs = TimeZone.getAvailableIDs(timeZone.getRawOffset());
						for (String availableID : availableIDs)
						{
							TimeZone zone = TimeZone.getTimeZone(availableID);
							if (zone.getDSTSavings() == dstSaving)
							{
								// this is a best guess... still the start and end of the DST should
								// be needed to know to be completely correct, or better yet
								// not just the GMT offset but the TimeZone ID should be transfered
								// from the browser.
								timeZone = zone;
								break;
							}
						}
					}

If dstTimeZone.getRawOffset() < timeZone.getRawOffset() then dstSaving is negative and it would never find any zone in the availableIDs.

I'm sending a PR for this.

Issue Links

• links to: GitHub Pull Request #377