总结的几个关于时间的方法。

//获取当地时间
- (NSString *)getCurrentTime {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy-MM-dd"];
    NSString *dateTime = [formatter stringFromDate:[NSDate date]];
    return dateTime;
}
//将字符串转成NSDate类型
- (NSDate *)dateFromString:(NSString *)dateString {
    
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat: @"yyyy-MM-dd"];
    NSDate *destDate= [dateFormatter dateFromString:dateString];
    return destDate;
}
//传入今天的时间，返回明天的时间
- (NSString *)GetTomorrowDay:(NSDate *)aDate {
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    NSDateComponents *components = [gregorian components:NSCalendarUnitWeekday | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:aDate];
    [components setDay:([components day]+1)];
    
    NSDate *beginningOfWeek = [gregorian dateFromComponents:components];
    NSDateFormatter *dateday = [[NSDateFormatter alloc] init];
    [dateday setDateFormat:@"yyyy-MM-dd"];
    return [dateday stringFromDate:beginningOfWeek];
}