很实用的Android日期计算类

package com.utils.datecount; 
 
import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.GregorianCalendar; 
 
public class DateCount { 
 
 /** 
  * datelevel 0为7天内，1为7到15天，2为15天以上 
  */ 
 public static int datelevel = 0; 
 public static int positionweek = -1; 
 public static int position2week = -1; 
  
 /** 
  * 获取与今天时间差 
  * @param endTime 
  * @return 
  */ 
 public static double countDate(String startTime) { 
   
  Date curDate = new Date(System.currentTimeMillis());// 获取当前时间 
  SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");// 输入日期的格式 
  Date date = null; 
   try { 
    date = simpleDateFormat.parse(startTime); 
    if (date == null) return 0; 
   } catch (java.text.ParseException e) { 
    return 0; 
//    e.printStackTrace(); 
   } 
  GregorianCalendar cal1 = new GregorianCalendar(); 
  GregorianCalendar cal2 = new GregorianCalendar(); 
  cal1.setTime(date); 
  cal2.setTime(curDate); 
  double dayCount = (cal2.getTimeInMillis() - cal1.getTimeInMillis()) / (1000 * 3600 * 24);// 从间隔毫秒变成间隔天数 
  return dayCount; 
 } 
} 

package com.utils.tools; 
 
import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Date; 
 
import android.text.TextUtils; 
import android.text.format.DateFormat; 
 
/** 
 * 日期格式化工具类 
 * 
 * @author Harryxu 
 * 
 */ 
public class DateUtil { 
  
 public static Date convert2Date(String format, String dateStr) { 
  Date date = null; 
  try { 
   if (TextUtils.isEmpty(format)) format = "yyyy-MM-dd HH:mm:ss"; 
   return new java.sql.Date(new SimpleDateFormat(format).parse(dateStr).getTime()); 
  } catch (IllegalArgumentException e) { 
   e.printStackTrace(); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } 
  return date; 
 } 
 
 public static CharSequence formatDate(String format, String dateStr) { 
  Date date = null; 
  try { 
   date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(dateStr); 
  } catch (IllegalArgumentException e) { 
   e.printStackTrace(); 
  } catch (Exception e) { 
   e.printStackTrace(); 
  } 
  if (date == null) date = new Date(); 
  if (TextUtils.isEmpty(format)) format = "yyyy-MM-dd"; 
  return DateFormat.format(format, date); 
 } 
 
 /** 
  * 根据偏量值取得传入时间的前后天数 
  * 
  * @param date 
  * @param offset 时间偏量值 
  * @return 
  */ 
 public static Date getNextPreDay(Date date, int offset) { 
  Calendar calendar = Calendar.getInstance(); 
  calendar.setTime(date); 
  calendar.add(Calendar.DAY_OF_MONTH, offset); 
  date = calendar.getTime(); 
  return date; 
 } 
  
 public static int getDays(Date date1, Date date2) { 
  Date kaishi = date1, jieshu = date2; 
  if (date1.compareTo(date2) > 0) { 
   kaishi = date2; 
   jieshu = date1; 
  } 
   
  long diff = jieshu.getTime() - kaishi.getTime(); 
  float days = diff / 24f / 60 / 60 / 1000; 
  return (int) ((days - (int) days) >= 0 ? (days + 1) : days); 
 } 
  
 public static String addMinites( String time, int addminite){ 
  SimpleDateFormat myFormatter = new SimpleDateFormat("HH:mm");  
  Calendar totime = Calendar.getInstance(); 
  java.util.Date date = null; 
  try { 
   date = myFormatter.parse(time); 
  } catch (ParseException e) { 
   e.printStackTrace(); 
  } 
  if (date == null) return null; 
  totime.setTime(date); 
  totime.add(Calendar.MINUTE, addminite); 
  date = totime.getTime(); 
  return myFormatter.format(date); 
   
 } 
}