ISO 8601 format used by OffsetDateTime.class

//精确到秒
String nowTime = OffsetDateTime.of(LocalDateTime.of(LocalDate.now(), LocalTime.now().withNano(0)), ZoneOffset.UTC).format(DateTimeFormatter.ISO_OFFSET_DATE_TIME);
//精确到天
String now00Time = OffsetDateTime.of(LocalDateTime.of(LocalDate.now(), LocalTime.MIN), ZoneOffset.UTC).format(DateTimeFormatter.ISO_OFFSET_DATE_TIME);

System.out.println(nowTime);
System.out.println(now00Time);

运行结果
2022-02-22T17:42:46Z
2022-02-22T00:00:00Z