js获取当前日期的前一天、一月、一年的日期
//获得当前日期昨天的日期     
unction getYestoday(date){         
   var yesterday_milliseconds=date.getTime()-1000*60*60*24;          
   var yesterday = new Date();          
       yesterday.setTime(yesterday_milliseconds);          
          
   var strYear = yesterday.getFullYear();       
   var strDay = yesterday.getDate();       
   var strMonth = yesterday.getMonth()+1;     
   if(strMonth<10)       
   {       
       strMonth="0"+strMonth;       
   }       
   datastr = strYear+"-"+strMonth+"-"+strDay;     
   return datastr;     
}     
      
//获得上个月在昨天这一天的日期     
function getLastMonthYestdy(date){     
    var daysInMonth = new Array([0],[31],[28],[31],[30],[31],[30],[31],[31],[30],[31],[30],[31]);     
    var strYear = date.getFullYear();       
    var strDay = date.getDate();       
    var strMonth = date.getMonth()+1;     
    if(strYear%4 == 0 && strYear%100 != 0){     
       daysInMonth[2] = 29;     
    }     
    if(strMonth - 1 == 0)     
    {     
       strYear -= 1;     
       strMonth = 12;     
    }     
    else    
    {     
       strMonth -= 1;     
    }     
    strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];     
    if(strMonth<10)       
    {       
       strMonth="0"+strMonth;       
    }     
    if(strDay<10)       
    {       
       strDay="0"+strDay;       
    }     
    datastr = strYear+"-"+strMonth+"-"+strDay;     
    return datastr;     
}     
      
//获得上一年在昨天这一天的日期     
function getLastYearYestdy(dat