JDK 1.8 DateTimeFormatter f = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS"); LocalDateTime ldt = LocalDateTime.parse("2023-01-01 00:00:00.123", f); System.out.println(ldt.plusNanos(1000000L).format(f)); System.out.println(ldt.plus(1L, ChronoUnit.MILLIS).format(f)); 결과 2023-01-01 00:00:00.124 2023-01-01 00:00:00.124 찾아보니 없어서 직접 질문했다. https://stackoverflow.com/questions/75866488/localdate..