在软件开发中，我们会经常遇到各种时间的显示及判断，这就需要我们对获取的数据进行转换。

“yyyy-MM-dd HH:mm:ss” 这是常用的时间显示格式，表示了“年-月-日 时:分:秒”

注意：HH表示24小时制，hh表示12小时制

1、日期字符串转换Date实体

public static Date parseServerTime(String serverTime, String format) {
    if (format == null || format.isEmpty()) {
        format = "yyyy-MM-dd HH:mm:ss";
    }
    SimpleDateFormat sdf = new SimpleDateFormat(format, Locale.CHINESE);
    sdf.setTimeZone(TimeZone.getTimeZone("GMT+8:00"));
    Date date = null;
    try {
        date = sdf.parse(serverTime);
    } catch (Exception e) {
        Timber.e(e, "");
    }
    return date;
}

参数一：时间字符串； 参数二：日期格式

2、秒数转换成时分秒

public static String convertSecToTimeString(long lSeconds) {
    long nHour = lSeconds / 3600;
    long nMin = lSeconds % 3600;
    long nSec = nMin % 60;
    nMin = nMin / 60;

    return String.format("%02d小时%02d分钟%02d秒", nHour, nMin, nSec);
}

3、Date对象获取时间字符串

public static String getDateStr(Date date,String format) {
    if (format == null || format.isEmpty()) {
        format = "yyyy-MM-dd HH:mm:ss";
    }
    SimpleDateFormat formatter = new SimpleDateFormat(format);
    return formatter.format(date);
}

4、时间戳转换日期格式字符串

public static String timeStamp2Date(long time, String format) {
    if (format == null || format.isEmpty()) {
        format = "yyyy-MM-dd HH:mm:ss";
    }
    SimpleDateFormat sdf = new SimpleDateFormat(format);
    return sdf.format(new Date(time));
}

5、日期格式字符串转换时间戳

public static String date2TimeStamp(String date, String format) {
    try {
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        return String.valueOf(sdf.parse(date).getTime() / 1000);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return "";
}

6、获取某个日期前后N天的日期

/**
 * 获取某个日期前后N天的日期
 *
 * @param beginDate
 * @param distanceDay 前后几天 如获取前7天日期则传-7即可；如果后7天则传7
 * @param format      日期格式，默认"yyyy-MM-dd"
 * @return
 */
public static String getOldDateByDay(Date beginDate, int distanceDay, String format) {
    if (format == null || format.isEmpty()) {
        format = "yyyy-MM-dd";
    }
    SimpleDateFormat dft = new SimpleDateFormat(format);
    Calendar date = Calendar.getInstance();
    date.setTime(beginDate);
    date.set(Calendar.DATE, date.get(Calendar.DATE) + distanceDay);
    Date endDate = null;
    try {
        endDate = dft.parse(dft.format(date.getTime()));
    } catch (Exception e) {
        e.printStackTrace();
    }
    return dft.format(endDate);
}

7、获取前后几个月的日期

/**
 * 获取前后几个月的日期
 * @param beginDate
 * @param distanceMonth
 * @param format
 * @return
 */
public static String getOldDateByMonth(Date beginDate, int distanceMonth, String format) {
    if (format == null || format.isEmpty()) {
        format = "yyyy-MM-dd";
    }
    SimpleDateFormat dft = new SimpleDateFormat(format);
    Calendar date = Calendar.getInstance();
    date.setTime(beginDate);
    date.set(Calendar.MONTH, date.get(Calendar.MONTH) + distanceMonth);
    Date endDate = null;
    try {
        endDate = dft.parse(dft.format(date.getTime()));
    } catch (Exception e) {
        e.printStackTrace();
    }
    return dft.format(endDate);
}

8、判断一个时间是否在某个时间范围内

 public static boolean isCurrentInTimeScope(int deadlineHour, int deadlineMin) {
     boolean result;
     // 1000 * 60 * 60 * 24
     final long aDayInMillis = 86400000;
     final long currentTimeMillis = SntpClock.currentTimeMillis();
     //截止时间
     Time deadlineTime = new Time();
     deadlineTime.set(currentTimeMillis);
     deadlineTime.hour = deadlineHour;
     deadlineTime.minute = deadlineMin;
     //当前时间
     Time startTime = new Time();
     startTime.set(currentTimeMillis);
     //当前时间推后20分钟
     Date d = new Date(currentTimeMillis);
     long myTime = (d.getTime() / 1000) + 20 * 60;
     d.setTime(myTime * 1000);
     Time endTime = new Time();
     endTime.set(myTime);
     if (!startTime.before(endTime)) {
         // 跨天的特殊情况（比如22:00-8:00）
         startTime.set(startTime.toMillis(true) - aDayInMillis);
         result = !deadlineTime.before(startTime) && !deadlineTime.after(endTime); 
         // startTime <= deadlineTime <=endTime
         Time startTimeInThisDay = new Time();
         startTimeInThisDay.set(startTime.toMillis(true) + aDayInMillis);
         if (!deadlineTime.before(startTimeInThisDay)) {
             result = true;
         }
     } else {
         // 普通情况(比如 8:00 - 14:00)
         result = !deadlineTime.before(startTime) && !deadlineTime.after(endTime);
         // startTime <= deadlineTime <=endTime
        }
        return result;
    }