很簡單，記錄一下
- (NSString *)beforeDate:(NSInteger)n {
NSDate *currentDate = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd"];
NSString *nowDateStr = [formatter stringFromDate:currentDate];
NSLog(@"當(dāng)前日期：%@",nowDateStr);
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *lastMonthComps = [[NSDateComponents alloc] init];
// [lastMonthComps setYear:1]; // year = 1表示1年后的時(shí)間 year = -1為1年前的日期，month day 類推
[lastMonthComps setMonth:n];
NSDate *newdate = [calendar dateByAddingComponents:lastMonthComps toDate:currentDate options:0];
NSString *beforeDateStr = [formatter stringFromDate:newdate];
return beforeDateStr;
}
