类似微信朋友圈将时间变成多少分钟、多少小时之前

//原理是把你手机上的即时时间全部和1970年比较变成多少秒，然后将你所传进来的时间参数同样这样处理，然后得出相差的秒，最后把相差的秒算出来就可以得到几分钟、几小时、或者几天前啦，这个文字可以自己做修改~
+ (NSString *)intervalSinceNow: (NSString *) theDate
{

NSDateFormatter *date=[[NSDateFormatter alloc] init];
[date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *d=[date dateFromString:theDate];

NSTimeInterval late=[d timeIntervalSince1970]*1;

NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];
NSTimeInterval now=[dat timeIntervalSince1970]*1;
NSString *timeString=@"";

NSTimeInterval cha=now-late;

if (cha/3600<1) {
timeString = [NSString stringWithFormat:@"%f", cha/60];
timeString = [timeString substringToIndex:timeString.length-7];
timeString=[NSString stringWithFormat:@"%@分钟前", timeString];
if ([timeString  isEqual: @"0分钟前"]) {
timeString = @"刚刚";
}
}
if (cha/3600>1&&cha/86400<1) {
timeString = [NSString stringWithFormat:@"%f", cha/3600];
timeString = [timeString substringToIndex:timeString.length-7];
timeString=[NSString stringWithFormat:@"%@小时前", timeString];
}
if (cha/86400>1)
{
//        timeString = [NSString stringWithFormat:@"%f", cha/86400];
//        timeString = [timeString substringToIndex:timeString.length-7];
//        timeString=[NSString stringWithFormat:@"%@天前", timeString];
timeString = theDate;

}
return timeString;
}