LocalDateTime获取当天、本周、本月的开始和结束时间、年总天数和年总周数

// 获取当天日期
LocalDate now = LocalDate.now();

// 当天开始时间
LocalDateTime todayStart = now.atStartOfDay();
// 当天结束时间
LocalDateTime todayEnd = LocalDateTime.of(now, LocalTime.MAX);

// 周一
LocalDate monday = now.with(TemporalAdjusters.previousOrSame(DayOfWeek.MONDAY));
// 周日
LocalDate sunday = now.with(TemporalAdjusters.nextOrSame(DayOfWeek.SUNDAY));

// 本周开始时间
LocalDateTime weekStart = monday.atStartOfDay();
// 本周结束时间
LocalDateTime weekEnd = LocalDateTime.of(sunday, LocalTime.MAX);

// 本月1号
LocalDate firstDayOfMonth = now.with(TemporalAdjusters.firstDayOfMonth());
// 本月最后一天
LocalDate lastDayOfMonth = now.with(TemporalAdjusters.lastDayOfMonth());
LocalDateTime firstDayOfMonthStart = firstDayOfMonth.atStartOfDay();
LocalDateTime firstDayOfMonthEnd = LocalDateTime.of(lastDayOfMonth, LocalTime.MAX);

// 年总天数
int lengthOfYear = now.lengthOfYear();
// 年总周数
WeekFields weekFields = WeekFields.of(DayOfWeek.MONDAY, 4);
int num = now().with(TemporalAdjusters.lastDayOfYear()).get(weekFields.weekOfWeekBasedYear());

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
System.out.println("当天开始时间 = " + todayStart.format(pattern) + 
"  时间戳 ：" + todayStart.toInstant(ZoneOffset.of("+8")).toEpochMilli());

System.out.println("当天结束时间 = " + todayEnd.format(pattern) + 
"  时间戳 ：" + todayEnd.toInstant(ZoneOffset.of("+8")).toEpochMilli());

System.out.println("本周开始时间 = " + weekStart.format(pattern) +
 "  时间戳 ：" + weekStart.toInstant(ZoneOffset.of("+8")).toEpochMilli());
 
System.out.println("本周结束时间 = " + weekEnd.format(pattern) + 
"  时间戳 ：" + weekEnd.toInstant(ZoneOffset.of("+8")).toEpochMilli());

System.out.println("本月开始时间 = " + firstDayOfMonthStart.format(pattern) + 
"  时间戳 ：" + firstDayOfMonthStart.toInstant(ZoneOffset.of("+8")).toEpochMilli());

System.out.println("本月结束时间 = " + firstDayOfMonthEnd.format(pattern) + 
"  时间戳 ：" + firstDayOfMonthEnd.toInstant(ZoneOffset.of("+8")).toEpochMilli());

来源：https://blog.csdn.net/m0_53556997/article/details/128329523