Most photo management solutions, including Apple’s iPhoto and Aperture applications, use the date and time that a picture was actually taken rather than a simple file date to arrange photos by date. This EXIF date is embedded in the JPEG files themselves and is unrelated to the normal file system creation and modification dates that you may see in the Finder.

While it’s great to arrange photos by the time they were shot, it can cause serious inconvenience when your camera’s internal clock is out of sync.. your photos will not appear in the correct order and your photo library will quickly become disorganized.

Amateurs and professionals alike occasionally forget to set their camera’s internal clock correctly, but by far the most common problems occur when travelling to another time zone (whether you’re on your honeymoon or reporting from a distant war zone) and when using multiple cameras.

Failing to adjust your camera’s time zone while on honeymoon may mean that the pictures that you’ve taken at breakfast on the 20th of January may actually be filed under the 19th around 10PM. Professional photographers often use a variety of different cameras fitted out with different lenses to cover the same event. Say a wide-angle lens for taking group pictures at a wedding and a 50mm lens for the portraits of the bride and groom. When the clocks of both cameras are out of sync (and when aren’t they?) the “cutting of the cake” pictures will end up interspersed with the “best man’s toast” and can cause a lot of extra work.

Adjusting the EXIF timestamp is by no means easily achieved. This data is written in stone (why would you want to change the time from the actual time to some ficitious time anyway?) and programs that allow you to edit (or better yet batch edit) this timestamp are very rare indeed.

Enter A Better Finder Attributes 4.4 and its ability to easily and conveniently batch adjust EXIF timestamps.

In this short tutorial, we’ll take some pictures and “fix” their timestamps. We’ll assume that we’re using iPhoto, but it could be any other photo application.

Don’t mess with the photo library

The first step is to locate the pictures we want to modify. This point is important, so let’s spell it out in bold:

Don’t modify the timestamp of the pictures that are already in iPhoto!

Work on copies instead.

iPhoto and other photo organization tools arrange your photos into their own folder hierarchy and you should never mess around with this or you risk losing precious meta-data and experiencing problems working with the files.

We have two options:

• if the photos are not yet in the library, we can perform the changes before importing them
• if the photos are already in the library, we must first export them before changing them and then re-importing the corrected files

Whatever else you do: keep the original files safe somewhere and correct the timestamp of the copies. That way you’ll never lose a photo.

Importing photos without iPhoto

If you know that the photos have incorrect timestamps, it is probably easier to correct their timestamp before importing them into iPhoto. How can you do this, since you use iPhoto to import the photos in the first place?

The solution is simple. Mac OS X comes with a little known image importing utility that uses the same code as iPhoto itself: Image Capture

You can find this nifty tool pre-installed in your “Applications” folder.

Apple have a brief description of how to use this tool on their Help website and I have covered using it previously in a tutorial on how to automatically give your iPhoto files meaningful names using A Better Finder Rename.

Exporting your photos from iPhoto

If your photos are already in iPhoto, you need to first export them before changing them.

This is easily achieved by using iPhoto’s “File” -> “Export…” feature:

Keep the default values which will make sure that the original files are exported.

Changing the EXIF timestamps

First locate your exported or freshly imported image files.
Then make copies of them and keep them somewhere safe

Now for the sake of argument, let’s say we need to add precisely 6 hours (we’ve crossed 6 timezones) and 15 seconds (this is our second camera and its clock was 15 seconds slow compared to the first camera).

First we launch A Better Finder Attributes. (Just click here, if you haven’t downloaded it yet).

The dialog below will appear:

Now drag and drop your photo files into the preview table on the right:

Then select “Add or remove time from the date a JPEG photo was taken” from the “Action:” popup menu and fill in the dialog with the appropriate values:

Note that you need to check the “I accept full responsibility for using this feature” checkbox before you can proceed. This is another gentle reminder that you shoud back up your files before messing around with them 🙂

Finally click the “OK” button and the EXIF dates are changed:

Voila!

Optionally delete the photos with incorrect timestamps from the iPhoto library

Hands down the best time to change EXIF dates is before you first import them into iPhoto. If this is no longer an option, you need to decide whether you want to keep the files with the incorrect timestamps or want to permanently erase them.

If you choose to erase them, your photo library will be in pristine condition with all photos arranged in correct chronological order, but you could potentially lose changes (effects, etc) to the files that you’ve already made in iPhoto. iPhoto is generally fairly good at dealing with this kind of thing, but I can’t vouch for it.. If you don’t erase the old photos you’ll end up with duplicates (the photo with the correct date and the original photo).

If you choose to remove the files from the iPhoto library, do so within iPhoto (pressing the Backspace key will transfer the selected pictures to the iPhoto trash). Never use the Finder to directly erase files within iPhoto’s Finder folder hierarchy!

Import your modified photos (back) into iPhoto

Choose “File” -> “Import to Library…” in iPhoto, locate your files and confirm the import.

Conclusions

As we’ve seen in this tutorial, changing EXIF dates with A Better Finder Attributes 4.4 is simple, but you have to be careful to let your photo management software know about it.

Most professionals will tend to use Image Capture, sometimes along with a few automatic scripts to import their files onto their Mac because this offers greater flexibility. If this interests you, you might like to read the already mentioned tutorial showing you how to use your own custom naming scheme with Image Capture automation.

I hope you will find this mini-tutorial useful.