I think the issue relates to not properly encoding the URL, so the web server isn't seeing the date you want:
NSString *url = [NSString stringWithFormat:@"http://ipadress/web_service/list.php?DATE=%@",dateSinc];
NSString *encodedURL = [url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSMutableURLRequest *request =[[[NSMutableURLRequest alloc] init] autorelease];
[request setURL:[NSURL URLWithString:encodedURL]];
// etc.