为什么java.sql.Date.getTime（）对于1970-01-02返回82_800_000而不是86_400_000？

Question

One day has 86400 seconds. Many time objects are related to the Epoch on 1970-01-01. The API says

A thin wrapper around a millisecond value that allows JDBC to identify this as an SQL DATE value. A milliseconds value represents the number of milliseconds that have passed since January 1, 1970 00:00:00.000 GMT

The following code returns 82800000. Why? What is wrong?

java.sql.Date sqlDate = java.sql.Date.valueOf( "1970-01-02" );
long millis = sqlDate.getTime();
System.out.println( "expected=" + 86400000 + " " + sqlDate
            + "\n  result=" + millis );

Answer 1

A milliseconds value represents the number of milliseconds that have passed since January 1, 1970 00:00:00.000 GMT

So if your time zone is GMT+1, you will get 82800000 for January 2, 1970:

(January 1, 1970 + one day - one hour)

Answer 2

Since you're living in Germany, your timezone is CET (or GMT+1 )

You're parsing the date corresponding to your own timezone so there'll be a difference of one hour between the value you're parsing and the initial beginning.

That said, the instant is the same.