如何判斷兩個時間是否是同一天

+ (BOOL)isCurrentDay:(NSDate *)aDate
{
    if (aDate==nil) return NO;
    
    NSCalendar *cal = [NSCalendar currentCalendar];
    NSDateComponents *components = [cal components:(NSEraCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:[NSDate date]];
    NSDate *today = [cal dateFromComponents:components];
    components = [cal components:(NSEraCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:aDate];
    NSDate *otherDate = [cal dateFromComponents:components];
    if([today isEqualToDate:otherDate])
        return YES;
    
    return NO;
}