首先蒙揣，獲得兩個比較的日期
//創(chuàng)建時間格式
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *fromDate = [dateFormatter dateFromString:@"2017-01-09 12:02:03"];
NSDate *toDate = [NSDate date];
比較兩個日期是否為同一天：
//判斷是否為同一天
- (BOOL)isSameDay:(NSDate*)date1 date2:(NSDate*)date2
{
NSCalendar* calendar = [NSCalendar currentCalendar];
unsigned unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth |? NSCalendarUnitDay;
NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date1];
NSDateComponents* comp2 = [calendar components:unitFlags fromDate:date2];
return [comp1 day]? == [comp2 day] &&
[comp1 month] == [comp2 month] &&
[comp1 year]? == [comp2 year];
}
相隔多少天
//NSCalendarIdentifierGregorian 公歷
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
//設定每周的第一天從星期幾開始守伸，比如:如需設定從星期日開始，則value傳入1;如需設定從星期一開始讥邻，則value傳入2
[gregorian setFirstWeekday:2];
NSDateComponents *dayComponents = [gregorian components:NSCalendarUnitDay fromDate:fromDate toDate:toDate options:0];
if (labs(dayComponents.day) >= 1) {
//進行檢測更新
}
關于NSDateComponents的講解，可以查看https://my.oschina.net/yongbin45/blog/156181的介紹
