Time is fundamental to the physical sciences, especially Astronomy.  Observers all over the world report results in (or referenced to)  UTC (Coordinated Universal Time)  which has now 'officially' replaced the  'historic'  GMT (Greenwich Mean Time).  Predictions are also typically in UTC, but it is worth double checking this.  Where you see times listed in “UT”, this 'could' mean UTC or UT1;  in practice it is often (not always) OK to use UTC.  All these time systems use a 24 hour clock.

In Hong Kong, the   Hong Kong (Observatory) Time Service   web site contains full information on the services available and useful background material.

In New Zealand time is maintained by the  Measurement Standards Laboratory   in the left frame select  Time and Frequency Standards  

New Zealand Standard Time is UTC + 12 hours throughout the whole country.

From the first Sunday in October to the third Sunday in March each year, New Zealand is on Daylight Saving Time of GMT +13 hours.  It may seem strange to have a time offset from GMT with an absolute value greater than 12 hours.   NOTE that this unusual NZ Daylight Saving (Summer) Time zone:  GMT + 13   differs by one day from the time zone  GMT - 11.

In Australia time is maintained by the  National Measurement Institute  (formerly the CSIRO National Measurement Laboratory)  -  go to the Capabilities tab and see their section on   Time and Frequency Capabilities      

The different   Australian Standard Time zones   are based on UTC, adjusted for longitude.  For example:  AEST = Australian Eastern Standard Time  =  UTC  +  10 hours  (centred on 150° East longitude) is used in Queensland, New South Wales, the ACT, Victoria and Tasmania.    South Australia and the Northern Territory use ACST = Australian Central Standard Time = UTC + 9 1/2 hours, and Western Australia uses AWST = Australian Western Standard Time = UTC + 8 hours.

Daylight Saving ("Summer") Time is the standard zone time + 1 hour.   NOTE:  Queensland, Western Australia and the Northern Territory do not observe Daylight Saving  -  it is a political issue.

All these civil time systems are now based on UTC, so that in all the different time "zones", the precise start of each second and minute are aligned with UTC.

When converting between local time and UTC, be aware that the your local "day" is often different from the UTC "day".  As one (Australian) example: if an event is  predicted on July 6 at 16h 15m UT (UTC),  then in the Eastern Australian winter the time will be 16:15 UTC + 10h = 26:15 AEST  (more than 24) =  02:15 AEST on the next day, which is  2:15 am on July 7, and not July 6.

Knowing your local time, you can also work backwards and find UTC by subtracting the 10, 11, 12 or 13 hours, again making sure you keep track of the day as well:
Example 1:   7:56 pm AEST = 19:56 AEST = 09:56 UTC  on the same day
Example 2:   3:22 am AEST = 03:22 AEST = 27:22 AEST previous day = 17:22 UTC previous day.

There are many UTC related web resource pages on the Internet, such as the one by  Brian Webb (USA) which contains a useful list of currently still (!....) operating time standard radio stations.