- (BOOL)setDateDigitized:(NSDate *)date forPhotoWithURL:(NSURL *)URL;
{
    CGImageSourceRef source = CGImageSourceCreateWithURL( (CFURLRef) URL,NULL);
    if (!source)
    {
        NSLog(@"***Could not create image source ***");
        return NO;
    }
    
    //get all the metadata in the image
    NSDictionary *metadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source,0,NULL);
    
    //make the metadata dictionary mutable so we can add properties to it
    NSMutableDictionary *metadataAsMutable = [[metadata mutableCopy]autorelease];
    [metadata release];
    
    NSMutableDictionary *EXIFDictionary = [[[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyExifDictionary]mutableCopy]autorelease];
    
    if(!EXIFDictionary)
    {
        //if the image does not have an EXIF dictionary (not all images do), then create one for us to use
        EXIFDictionary = [NSMutableDictionary dictionary];
    }
    
    
    //we need to format the date so it conforms to the EXIF spec and can be read by other apps
	
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    [dateFormatter setFormatterBehavior:NSDateFormatterBehavior10_4];
    [dateFormatter setDateFormat:@"yyyy:MM:dd HH:mm:ss"]; //the date format for EXIF dates as from http://www.abmt.unibas.ch/dokumente/ExIF.pdf
    NSString *EXIFFormattedCreatedDate = [dateFormatter stringFromDate:date]; //use the date formatter to get a string from the date we were passed in the EXIF format
    [dateFormatter release];
    
    [EXIFDictionary setObject:EXIFFormattedCreatedDate forKey:(NSString *)kCGImagePropertyExifDateTimeDigitized];
    
    
    //add our modified EXIF data back into the imageÕs metadata
    [metadataAsMutable setObject:EXIFDictionary forKey:(NSString *)kCGImagePropertyExifDictionary];
    
    CFStringRef UTI = CGImageSourceGetType(source); //this is the type of image (e.g., public.jpeg)
    
    //this will be the data CGImageDestinationRef will write into
    NSMutableData *data = [NSMutableData data];
    
    CGImageDestinationRef destination = CGImageDestinationCreateWithData((CFMutableDataRef)data,UTI,1,NULL);
    
    if(!destination)
    {
        NSLog(@"***Could not create image destination ***");
        return NO;
    }
    
    //add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
    CGImageDestinationAddImageFromSource(destination,source,0, (CFDictionaryRef) metadataAsMutable);
    
    //tell the destination to write the image data and metadata into our data object.
    //It will return false if something goes wrong
    BOOL success = NO;
    success = CGImageDestinationFinalize(destination);
    
    if(!success)
    {
        NSLog(@"***Could not create data from image destination ***");
        return NO;
    }
    
    
    //now we have the data ready to go, so do whatever you want with it
    //here we just write it to disk at the same path we were passed
    [data writeToURL:URL atomically:YES];
    
    //cleanup
    CFRelease(destination);
    CFRelease(source);
    
    return YES;
}