The solution that is presented in this section will display the following information about the 15 hours and 30 minutes flight from Perth, Australia to Bucharest, Europe:

• UTC date-time at departure and arrival
• Perth date-time at departure and arrival in Bucharest
• Bucharest date-time at departure and arrival

Let's assume that the reference departure date-time from Perth is February 26, 2019, at 16:00 (or 4:00 PM):

LocalDateTime ldt = LocalDateTime.of(
  2019, Month.FEBRUARY, 26, 16, 00);

First, let's combines this date-time with the time zone of Australia/Perth (+08:00). This will result in a ZonedDateTime object that is specific to Australia/Perth (this is the clock date and time in Perth at departure):

// 04:00 PM, Feb 26, 2019 +0800 Australia/Perth
ZonedDateTime auPerthDepart 
  = ldt.atZone(ZoneId.of("Australia/Perth"));

Further, let's add 15 hours and 30 minutes to ZonedDateTime. The resulting ZonedDateTime represents the  date-time in Perth (this is the clock date and time in Perth on arrival in Bucharest):

// 07:30 AM, Feb 27, 2019 +0800 Australia/Perth
ZonedDateTime auPerthArrive 
  = auPerthDepart.plusHours(15).plusMinutes(30);

Now, let's calculate the date-time in Bucharest at the departure date-time in Perth. Basically, the following code expresses the departure date-time from the Perth time zone in the Bucharest time zone:

// 10:00 AM, Feb 26, 2019 +0200 Europe/Bucharest
ZonedDateTime euBucharestDepart 
  = auPerthDepart.withZoneSameInstant(ZoneId.of("Europe/Bucharest"));

Finally, let's calculate the date-time in Bucharest on arrival. The following code expresses the arrival date-time from the Perth time zone in the Bucharest time zone:

// 01:30 AM, Feb 27, 2019 +0200 Europe/Bucharest
ZonedDateTime euBucharestArrive 
  = auPerthArrive.withZoneSameInstant(ZoneId.of("Europe/Bucharest"));

As shown in the following figure, the UTC time at departure from Perth is 8:00 AM, while the UTC time on arrival in Bucharest is 11:30 PM:

These times can be easily extracted as OffsetDateTime, as follows:

// 08:00 AM, Feb 26, 2019
OffsetDateTime utcAtDepart = auPerthDepart.withZoneSameInstant(
  ZoneId.of("UTC")).toOffsetDateTime();

// 11:30 PM, Feb 26, 2019
OffsetDateTime utcAtArrive = auPerthArrive.withZoneSameInstant(
  ZoneId.of("UTC")).toOffsetDateTime();