【问题标题】：Calculate days, months, and years elapsed between start and end date [duplicate]计算开始日期和结束日期之间经过的天数、月数和年数[重复]
【发布时间】：2019-02-05 11:59:27
【问题描述】：

我正在开发日期计算应用程序，例如 Windows 10 计算器您在哪里选择开始和结束日期并计算年月日数

  public String differenceInDates(){
                Date start_date = convertStringToDate("2017-04-24");
                Date end_date = convertStringToDate("2018-07-24");
                long different = this.end_date.getTime() - this.start_date.getTime();

                        long millisInSeconds = 1000;
                        long millisInMinutes = millisInSeconds * 60;
                        long millisInHours = millisInMinutes * 60;
                        long millisInDay = millisInHours *24;

                        long elapsedDays = different / millisInDay;
                        different = different % millisInDay;

                        long elapsedHours = different / millisInHours;
                        different = different % millisInHours;

                        long elapsedMinutes = different / millisInMinutes;
                        different = different % millisInMinutes;

                        long elapsedSeconds = different / millisInSeconds;
                        if (elapsedHours == 0){
                            return String.valueOf("days"+elapsedDays+":"+":"+elapsedMinutes+":"+elapsedSeconds);
                        }
                        if (elapsedMinutes == 0){
                            return String.valueOf("days"+elapsedDays+":"+":"+elapsedHours+":"+elapsedSeconds);
                        }
                        if (elapsedHours == 0 && elapsedMinutes == 0){
                            return String.valueOf("days"+elapsedDays);
                        }
                        return String.valueOf("days"+elapsedDays+":"+" Hours"+elapsedHours+":"+" Minutes"+elapsedMinutes+":"+elapsedSeconds);
                }

                private Date convertStringToDate(String strDate) throws ParseException {
                        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
                        Date date = simpleDateFormat.parse(strDate);
                        return date;
                    }

我想要这样的答案

1 年 3 个月

【问题讨论】：

@fantaghirocco 不太一样。这个问题是关于年-月-日尺度的，而那个问题是关于时-分-秒尺度的。不同的问题有不同的解决方案。
仅供参考，非常麻烦的旧日期时间类，如 java.util.Date、java.util.Calendar 和 java.text.SimpleDateFormat 现在是 legacy，被 Java 8 中内置的 java.time 类所取代，之后。见Tutorial by Oracle。
也类似于：*Java 8: Calculate difference between two LocalDateTime

标签： java

【解决方案1】：

java.time

如果你可以使用LocalDate & Period，那就很简单了：

LocalDate date1 = LocalDateTime.of(2018, Month.SEPTEMBER, 2, 13, 40);
LocalDate date2 = LocalDateTime.of(2018, Month.SEPTEMBER, 2, 13, 40);
Period period = Period.between(date1, date2);
System.out.println(period.getYears() + " year " + period.getMonths() + " months");

【讨论】：

【解决方案2】：

您可以使用此代码：

SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
            String CURRDATE = "16-07-1991";
            String EFFDATE = "28-08-2018";

            Date startdate = null;
            Date enddate = null;
            try {
                startdate = formatter.parse(CURRDATE);
                enddate = formatter.parse(EFFDATE);
            } catch (ParseException e) {
                e.printStackTrace();
            }

            Calendar startCalendar = new GregorianCalendar();
            startCalendar.setTime(startdate);

            Calendar endCalendar = new GregorianCalendar();
            endCalendar.setTime(enddate);

            int monthCount = 0;
            int firstDayInFirstMonth = startCalendar.get(Calendar.DAY_OF_MONTH);
            startCalendar.set(Calendar.DAY_OF_MONTH, 1);
            endCalendar.add(Calendar.DAY_OF_YEAR, -firstDayInFirstMonth + 1);

            while (!startCalendar.after(endCalendar)) {
                startCalendar.add(Calendar.MONTH, 1);
                ++monthCount;
            }

            startCalendar.add(Calendar.MONTH, -1);
            --monthCount;
            int remainingDays = 0;
            while (!startCalendar.after(endCalendar)) {
                startCalendar.add(Calendar.DAY_OF_YEAR, 1);
                ++remainingDays;
            }

            startCalendar.add(Calendar.DAY_OF_YEAR, -1);
            --remainingDays;

            int lastMonthMaxDays = endCalendar.getActualMaximum(Calendar.DAY_OF_MONTH);
            if (remainingDays >= lastMonthMaxDays) {
                ++monthCount;
                remainingDays -= lastMonthMaxDays;
            }

            int diffMonth = monthCount % 12;
            int diffYear = monthCount / 12;
            int diffDay = remainingDays;

            System.out.println(diffYear + " Year(s) and " + diffMonth + " Month(s) and " + diffDay + " Day(s)");

结果是：

27 Year(s) and 1 Month(s) and 12 Day(s)

【讨论】：