怎么得到过了多长时间

如何得到过了多长时间！

public String getIntervalDays(Date startday, Date endday) {
??//确保startday在endday之前
??if (startday.after(endday)) {
???Date cal = startday;
???startday = endday;
???endday = cal;
??}
??//分别得到两个时间的毫秒数
??long sl = startday.getTime();
??long el = endday.getTime();

??long ei = el - sl;
??//根据毫秒数计算间隔天数
??int month=(int) (ei / (1000 * 60 * 60 * 24 * 12));
??int days=(int) (ei / (1000 * 60 * 60 * 24));
??int housrs=(int) (ei / (1000 * 60 * 60));
??int Minutes=(int) (ei / (1000 * 60 ));
??int ss=(int) (ei / (1000));
??if(ss<=60){
???return ss+" 秒钟前更新";
??}else if(Minutes<=60){
???return Minutes+" 分钟前更新";
??}else if(housrs<=24){
???return housrs+" 小时前更新";
??}else if(days<=30){
???return days+" 天前更新";
??}else{
???return month+" 月前更新";
??}
??
?}