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How to convert java.sql.timestamp to LocalDate (java8) java.time?

java
time-zone-differences
java-time-api
date-conversion
Alex KataevbyAlex Kataev·Dec 25, 2024
TLDR

The smallest, most effective way to convert java.sql.Timestamp to LocalDate is to use toLocalDateTime() and toLocalDate():

LocalDate localDate = timestamp.toLocalDateTime().toLocalDate(); //easy peasy lemon squeezy

This compact one-liner pulls out the date from a timestamp just like a hand in a magician's hat.

Accounting for time zone differences

Even though the approach above is quick and trouble-free, it turns a blind eye to time zones. The toLocalDateTime() method involves an underlying assumption of the system's default time zone. Should your application require compliance with a specific time zone, make sure this is handled directly:

LocalDate localDate = timestamp.toInstant() .atZone(ZoneId.of("UTC")) .toLocalDate(); //Because we all love UTC, don't we?

This piece of code guarantees that there's zero ambiguity during the conversion process, and time zone uniformity is maintained throughout your application.

Tackling precision and accuracy losses

Bear in mind that java.sql.Timestamp comes with nanosecond precision, which sadly isn't retained when converted to LocalDate. If your use case revolves around minute time details, consider if truncating to a date-only format works for you.

Keeping a tab on common slip-ups

Dealing with dates and timings typically amount to tricky bugs unless you keep a sharp eye out:

  • Time zone inconsistencies: The question "Is the system's default time zone what you really intended?" should always linger. Unwittingly using ZoneId.systemDefault() can lead to unpleasant surprises if your application shifts environments or the system time zone changes.

  • Data loss: A Timestamp can hold more than just a date. Converting to LocalDate inherently sheds time info; do this only when the loss isn't detrimental.

  • Fly-by-conversions: During database interfacing, it’s routine for apps to convert between java.sql.Timestamp and java.time. For accuracy, use java.time.ZonedDateTime or java.time.OffsetDateTime to encapsulate both date and time with a time zone offset.

Fine-tuning time zone settings

If you desire absolute precision, earmark a ZoneId during conversion. Here's how to convert a Timestamp to LocalDate in the UTC jurisdiction:

LocalDate utcDate = timestamp.toInstant() .atZone(ZoneId.of("UTC")) .toLocalDate(); // UTC rules!

Or, utilize the system default time zone:

LocalDate systemDefaultDate = timestamp.toInstant() .atZone(ZoneId.systemDefault()) .toLocalDate(); // Go with the flow of the system default

This way, the context is spelt out explicitly, bypassing any possible misinterpretations or assumptions.

Marching towards java.time

Java 8 introduced us to a hefty java.time API. It's a good practice to shift your application to use java.time types like Instant, LocalDate, and ZonedDateTime. Not only is their precision superior, they're also compatible beyond the older java.util.Date and java.sql.Timestamp. Making them immutable is the cherry on top, especially in a multithreaded environment.