iOS开发之计算当前时间的前几天，几个月，几年

这个方法很好的直接加上月份，不用考虑大小月问题

//得到当前的时间 NSDate * mydate = [NSDate date]; NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"yyyy-MM-dd"]; NSString *currentDateStr = [dateFormatter stringFromDate:[NSDate date]]; DebugLog(@"---当前的时间的字符串 =%@",currentDateStr); NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian]; NSDateComponents *comps = nil; comps = [calendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitMonth fromDate:mydate]; NSDateComponents *adcomps = [[NSDateComponents alloc] init]; [adcomps setYear:0]; [adcomps setMonth:-2]; [adcomps setDay:0]; NSDate *newdate = [calendar dateByAddingComponents:adcomps toDate:mydate options:0]; NSString *beforDate = [dateFormatter stringFromDate:newdate]; DebugLog(@"---前两个月 =%@",beforDate);