IOS比较两个日期的大小获取当前月份天数（今天、明天、后天）

/** 获取当前月份的最后一天 */
-(void)_getDateBtnValue
{
NSInteger year = [[NSDate date] getYear]; //获取年份
NSInteger month = [[NSDate date] getMonth];//获取月份
NSInteger day = [[NSDate date] getDay];//获取日期

//判断当前月分的天数
int endDate = 0;
switch (month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
endDate = 31;
break;
break;
case 4:
case 6:
case 9:
case 11:
endDate = 30;
break;
case 2:
// 是否为闰年
if (year % 400 == 0) {
endDate = 29;
break;
} else {
if (year % 100 != 0 && year %4 ==4) {
endDate = 29;
} else {
endDate = 28;
}
break;
}
break;
default:
break;
}

NSDictionary *dic =  [self calculateDateWithEndDate:endDate withDay:day withMonth:month];
dateDic = dic;
//更新Button内容
[self.todayBtn setTitle:[NSString stringWithFormat:@"今天(%@/%@)",dic[@"month"],dic[@"day"]] forState:UIControlStateNormal];
[self.tomorrowBtn setTitle:[NSString stringWithFormat:@"明天(%@/%@)",dic[@"tomorrowMonth"],dic[@"tomorrow"]] forState:UIControlStateNormal];
[self.afterDayBtn setTitle:[NSString stringWithFormat:@"后天(%@/%@)",dic[@"afterDayMonth"],dic[@"afterDay"]] forState:UIControlStateNormal];
}

/**
*  判断当前今天明天后天在跨月的时候天数和月份数
*  @parma endDate:当月最后一天
*  @parma day:今天的日期
*  @parma month:当前月份
*  @parma weekday:当前是周几
*/

-(NSDictionary *)calculateDateWithEndDate:(int)endDate withDay:(NSInteger)day withMonth:(NSInteger)month
{
NSInteger tomorrow = 0; //明天
NSInteger afterDay = 0;  //后天
NSInteger tomorrowMonth = 0;
NSInteger afterDayMonth = 0;
NSInteger currentYear = [[NSDate date] getYear];
NSInteger nextYear = currentYear;
NSInteger lastYear = nextYear;

if(endDate - day <= 0)
{
tomorrow = 1;
afterDay = tomorrow + 1;
tomorrowMonth = month + 1;
if(tomorrowMonth > 12)
{
tomorrowMonth = 1;
nextYear=nextYear + 1;
lastYear = nextYear;
}
afterDayMonth = tomorrowMonth;
}

else if(endDate - day == 1)
{
tomorrow = endDate;
afterDay = 1;
tomorrowMonth = month;
afterDayMonth = month + 1;
if(month == 12)
{
afterDayMonth = 1;
lastYear = nextYear + 1;
}
}

else
{
tomorrow = day+1;
afterDay = tomorrow + 1;
tomorrowMonth = month;
afterDayMonth = month;
}

NSMutableDictionary *dic = [NSMutableDictionary dictionary];
[dic setObject:[NSNumber numberWithInteger:day] forKey:@"day"];
[dic setObject:[NSNumber numberWithInteger:month] forKey:@"month"];
[dic setObject:[NSNumber numberWithInteger:currentYear] forKey:@"year"];

[dic setObject:[NSNumber numberWithInteger:tomorrow] forKey:@"tomorrow"];
[dic setObject:[NSNumber numberWithInteger:tomorrowMonth] forKey:@"tomorrowMonth"];
[dic setObject:[NSNumber numberWithInteger:nextYear] forKey:@"nextYear"];

[dic setObject:[NSNumber numberWithInteger:afterDay] forKey:@"afterDay"];
[dic setObject:[NSNumber numberWithInteger:lastYear] forKey:@"lastYear"];
[dic setObject:[NSNumber numberWithInteger:afterDayMonth] forKey:@"afterDayMonth"];

return dic;

}

/**
*  判断两个时间的大小
*  @parma selectDate:选择的日期
*  @return 1:大于当前日期 -1:小于当前时间 0:等于当前时间
*/
-(int)compareDateWithSelectDate:(NSString *)selectDate
{
NSDate *currentDate = [NSDate date];
NSDateFormatter *fomatter = [[NSDateFormatter alloc] init];
[fomatter setDateFormat:@"YYYY-MM-dd HH:mm"];
NSString *curentDateStr = [fomatter stringFromDate:currentDate];
currentDate = [fomatter dateFromString:curentDateStr];

int result = [[fomatter dateFromString:selectDate] compare:currentDate];
if(result == NSOrderedDescending)
{
return 1;
}
else if(result == NSOrderedAscending)
{
return -1;
}
return 0;
}

/** 获取今天是周几 **/
-(NSString *)_getWeakDay:(UIButton *)sender
{
NSInteger weakday = [[NSDate date] weekday];//周末为第一天
NSString *selectWeakDay = @"";
NSInteger tmpWeakday = weakday;
switch (sender.tag) {
case 100://今天
{
tmpWeakday = weakday;
}
break;
case 101://明天
{
tmpWeakday = weakday+1;
if(tmpWeakday>7)
{
tmpWeakday = 1;
}
}
break;
case 102://后天
{
tmpWeakday = weakday + 2;
if(tmpWeakday - 7 > 0)
{
(tmpWeakday == 8) ? (tmpWeakday = 1) : (tmpWeakday = 2);
}
}
break;
default:
break;
}

switch (tmpWeakday) {
case 1:
selectWeakDay = @"星期天";
break;

case 2:
selectWeakDay = @"星期一";
break;

case 3:
selectWeakDay = @"星期二";
break;

case 4:
selectWeakDay = @"星期三";
break;

case 5:
selectWeakDay = @"星期四";
break;

case 6:
selectWeakDay = @"星期五";
break;

case 7:
selectWeakDay = @"星期六";
break;
default:
break;
}

return selectWeakDay;
}