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From: "michalkoza (@michalkoza)" <noreply+michalkoza@github.com>
To: "pgjdbc/pgjdbc" <noreply+pgjdbc-pgjdbc@github.com>
Date: Wed, 07 Aug 2024 21:58:38 +0000
Subject: Re: [pgjdbc/pgjdbc] issue #1325: Additional jsr 310 support
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@marschall Conversion from java.sql.Timestamp -> Instant is independent of time zone. Check this code:
```java
TimeZone.setDefault(TimeZone.getTimeZone("America/Los_Angeles"));
LocalDateTime localDateTime = LocalDateTime.of(2018, 11, 16, 18, 2);
Timestamp timestamp = Timestamp.valueOf(localDateTime);
Instant instant1 = timestamp.toInstant();
System.out.println("timestamp in LA zone " + timestamp);
System.out.println("instant1  in LA zone " + instant1);

TimeZone.setDefault(TimeZone.getTimeZone("America/New_York"));
Instant instant2 = timestamp.toInstant();
System.out.println("timestamp in NY zone " + timestamp);
System.out.println("instant1  in NY zone " + instant1);
System.out.println("instant2  in NY zone " + instant2);
long epochMilli1 = instant1.toEpochMilli();
long epochMilli2 = instant2.toEpochMilli();
System.out.printf("epochMilli1: %d%n", epochMilli1);
System.out.printf("epochMilli2: %d%n", epochMilli2);
System.out.println("same instant: " + instant1.equals(instant2));
```

If you have a fixed timestamp, you can change time zones and convert it to Instant many times, always getting the same result. Observe also that even though the `timestamp` is never changed it is displayed differently depending on time zone, but it keeps the same value.

In your example the difference comes from the fact that 18:02 in LA is different moment in time than 18:02 in NY. It would be surprising if your Instants and Timestamps would be equal.

`Instant` is a moment in time in UTC. The same goes for `TIMESTAMP` type in PostgreSQL. They are both timezone-agnostic. So I struggle to understand why would you not want to store Instant as TIMESTAMP rather than TIMESTAMPTZ