Java 17 Recipes

4-13. Converting Dates and Times Based on he 
Time Zone
 Problem
The application you are developing has the potential to be utilized throughout the 
world. In some areas of the application, static dates and times need to be displayed, 
rather than the system date and time. In such cases, those static dates and times need to 
be converted to suit the particular time zone in which the application user is currently 
residing.
 Solution
The Date-Time API provides the proper utilities for working with time zone data 
via the Time Zone and Offset classes. In the following scenario, suppose that the 
application works with reservations for rental vehicles. You could rent a vehicle in one 
time zone and return it in another. The following lines of code demonstrate how to 
print out an individual’s reservation in such a scenario. The following method, named 
scheduleReport, accepts LocalDateTime objects representing check-in and check-out 
date/time, along with ZoneIds for each. An airline could use this method to print time 
zone information for a particular flight.
public static void scheduleReport(LocalDateTime checkOut, ZoneId checkOutZone,
LocalDateTime checkIn, ZoneId checkInZone){
Chapter 4 Numbers aNd dates

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134
ZonedDateTime beginTrip = ZonedDateTime.of(checkOut, checkOutZone);
System.out.println("Trip Begins: " + beginTrip);
// Get the rules of the check out time zone
ZoneRules checkOutZoneRules = checkOutZone.getRules();
System.out.println("Checkout Time Zone Rules: " + checkOutZoneRules);
//If the trip took 4 days
ZonedDateTime beginPlus = beginTrip.plusDays(4);
System.out.println("Four Days Later: " + beginPlus);
// End of trip in starting time zone
ZonedDateTime endTripOriginalZone = ZonedDateTime.of(checkIn, 
checkOutZone);
ZonedDateTime endTrip = ZonedDateTime.of(checkIn, checkInZone);
int diff = endTripOriginalZone.compareTo(endTrip);
String diffStr = (diff >= 0) ? "NO":"YES";
System.out.println("End trip date/time in original zone: " + 
endTripOriginalZone);
System.out.println("End trip date/time in check-in zone: " + endTrip );
System.out.println("Original Zone Time is less than new zone time? " +
diffStr );
ZoneId checkOutZoneId = beginTrip.getZone();
ZoneOffset checkOutOffset = beginTrip.getOffset();
ZoneId checkInZoneId = endTrip.getZone();
ZoneOffset checkInOffset = endTrip.getOffset();
System.out.println("Check out zone and offset: " + checkOutZoneId + 
checkOutOffset);
System.out.println("Check in zone and offset: " + checkInZoneId 
+ checkInOffset);
}
Here is the result.
Trip Begins: 2021-12-13T13:00-05:00[US/Eastern]
Checkout Time Zone Rules: ZoneRules[currentStandardOffset=-05:00]
Four Days Later: 2021-12-17T13:00-05:00[US/Eastern]
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135
End trip date/time in original zone: 2021-12-18T10:00-05:00[US/Eastern]
End trip date/time in check-in zone: 2021-12-18T10:00-07:00[US/Mountain]
Original Zone Time is less than new zone time? YES
Check out zone and offset: US/Eastern-05:00
Check in zone and offset: US/Mountain-07:00