How to convert ZonedDateTime to Date?

Question

I am trying to set a server agnostic date time in my database and I believe the best practice to do so is to set a UTC DateTime. My db server is Cassandra and the db driver

Answer 1

The accepted answer did not work for me. The Date returned is always the local Date and not the Date for the original Time Zone. I live in UTC+2.

//This did not work for me
Date.from(java.time.ZonedDateTime.now().toInstant()); 

I have come up with two alternative ways to get the correct Date from a ZonedDateTime.

Say you have this ZonedDateTime for Hawaii

LocalDateTime ldt = LocalDateTime.now();
ZonedDateTime zdt = ldt.atZone(ZoneId.of("US/Hawaii"); // UTC-10

or for UTC as asked originally

Instant zulu = Instant.now(); // GMT, UTC+0
ZonedDateTime zdt = zulu.atZone(ZoneId.of("UTC"));

Alternative 1

We can use java.sql.Timestamp. It is simple but it will probably also make a dent in your programming integrity

Date date1 = Timestamp.valueOf(zdt.toLocalDateTime());

Alternative 2

We create the Date from millis (answered here earlier). Note that local ZoneOffset is a must.

ZoneOffset localOffset = ZoneOffset.systemDefault().getRules().getOffset(LocalDateTime.now());
long zonedMillis = 1000L * zdt.toLocalDateTime().toEpochSecond(localOffset) + zdt.toLocalDateTime().getNano() / 1000000L;
Date date2 = new Date(zonedMillis);