//比较两个日期的大小 日期格式为2016-08-14 08：46：20
+ (NSInteger)compareDate:(NSString*)aDate withDate:(NSString*)bDate
{
NSInteger aa;
NSDateFormatter *dateformater = [[NSDateFormatter alloc] init];
[dateformater setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *dta = [[NSDate alloc] init];
NSDate *dtb = [[NSDate alloc] init];
dta = [dateformater dateFromString:aDate];
dtb = [dateformater dateFromString:bDate];
NSComparisonResult result = [dta compare:dtb];
if (result=NSOrderedSame)
{
// 相等 aa=0
}else if (result=NSOrderedAscending)
{
//bDate比aDate大
aa=1
}else if (result=NSOrderedDescending)
{
//bDate比aDate小
aa=-1
}
return aa;
}
