iOS计算两个NSDate间间隔天数

+(NSInteger)getDaysFrom:(NSDate *)serverDate To:(NSDate *)endDate
{
    NSCalendar *gregorian = [[NSCalendar alloc]
                             initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
   
    [gregorian setFirstWeekday:2];
  
   //去掉时分秒信息
    NSDate *fromDate;
    NSDate *toDate;
    [gregorian rangeOfUnit:NSCalendarUnitDay startDate:&fromDate interval:NULL forDate:serverDate];
    [gregorian rangeOfUnit:NSCalendarUnitDay startDate:&toDate interval:NULL forDate:endDate];
    NSDateComponents *dayComponents = [gregorian components:NSCalendarUnitDay fromDate:fromDate toDate:toDate options:0];

    return dayComponents.day;
}
简单方便， 跟实际理解一样。

日期相同就是同一天
日期差一天就是差一天，与是否满24小时无关