Validation request - how do databases and Java store and process time intervals?

Question

My apologies for the extremely simple question, I think I know the answer, but I want to confirm:

When you reference time zones and how they are usually stored in the database and in java.util.Date:

• When saving the date field in the database, this is the aggregated value of the time zone (for example, it is always saved in UTC format)
• When using a Java Date object, the date is also temporary agnostic
• The time zone depends only on the date of formatting and parsing (DB and Java)
• If you use Java, it will use the JVM user.timezone to format / parse dates
• If you use Java on Windows, Java will automatically take this from the regional settings.
• The database timezone (and machine timezone) is not related to the Java JDBC client
• The database server time zone is relevant only for direct SQL parsing and generation

My questions:

• Are all the above assumptions correct? some? All of them?
• Is there a reference / official source that confirms this more "officially"?

Answer 1

Assumptions are mostly true for Java. They are not necessarily correct for databases, since there are options.

Java handles time zones with calendar objects. The java.util.Date object always contains a UTC value.

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