this code converts timestamp to String

Timestamp timestamp = Timestamp.valueOf("2021-12-29 00:00:00");
       

System.out.println(FastDateFormat.getInstance("YYYY-MM-dd HH:mm:ss").format(timestamp));

The output of above code should be 2021-12-29 00:00:00 but got 2022-12-29 00:00:00

This happens with dates near to end of year