如何获取到给定时间的前一天和后一天

    NSString *dateString = @"2016-03-28";

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

    [formatter setDateFormat:@"yyyy-MM-dd"];

    NSDate *date = [formatter dateFromString:dateString];

    NSDate *yesterday = [NSDate dateWithTimeInterval:-60 * 60 * 24 sinceDate:date];

    NSDate *tomorrow = [NSDate dateWithTimeInterval:60 * 60 * 24 sinceDate:date];

    NSLog(@"yesterday %@    tomorrow %@", [formatter stringFromDate:yesterday], [formatter stringFromDate:tomorrow]);