We have just rolled out some changes to have changed user timezone settings from an offset (e.g. '+1200') to a named timezone e.g. 'Pacific/Auckland'.
If you have previously changed your timezone setting from the system default to a specific offset, and that offset didn't match NZ time (with or without daylight savings), the system upgrade would have tried to select a match for your given offset. Given that each offset potentially matches more than one location, it may not have selected a timezone that reflects your location. Please take a moment to go to 'My Account' -> 'Settings' and check your Locale settings.
The previous offset settings, being hardcoded values, were not working very well during daylight savings. For example, if you had a setting of +1200 (which is the default), you would have seen the system displaying timestamps for posts older than a day an hour behind (because the offset should actually be +1300 during daylight savings).
With the code changes accompanying the settings change, we have attempted to customise display of timestamps on posts and messages where possible to your chosen timestamp. Anything that is customised for your viewing should have its timestamp relative to your selected timezone. The exception is any bulk notification (e.g. newsletters, thread subscriptions) that go out to multiple users - those will still use the system timezone to display timestamps.
Let us know if there are any issues. Thanks.