The embedded date and time metadata hidden within digital photographs provide an excellent historical record that turns your photo collection into an effortless pictorial diary. One day, when historians (who might just be your children or grandchildren) are trying to piece together your life story, they will refer to this so-called 'EXIF metadata' within your snapshots as important clues in the puzzle. But metadata dates and times are only as accurate as the calendar and clock settings in the camera that took the pictures. Many people fail to adjust these settings correctly after purchasing a camera. Or perhaps the settings drift through various time-zones and across datelines while traveling, and have been neglected and forgotten.
In my case, a strong magnetic field corrupted my camera's date and time settings without my realising it. I was left with many months' worth of wrongly-dated pictures.
EXIF data is not normally edited once the photo has been taken, so it can be quite tricky to figure out how to fiddle with it. Thankfully solutions to this problem do exist and, best of all, there's no need to laboriously adjust each file individually.
Much of the following applies to the Windows operating system, so users of other systems will have to adapt this material using whatever software is available to them.
First of all, you might like to check the settings within your camera (if you still have it) and determine whether they are accurate. These settings will be accessible via your camera's setup menus. If the camera's date and time settings are off, the image files on your computer will likely be off by a similar amount.
Please note that the date and time recorded within a picture's EXIF metadata are quite different to the dates associated with the image files on your hard drive. All computer files have dates associated with them. The files themselves will simply reflect the date of their creation, modification, etc, which is probably a function of when you downloaded them from your camera. This event might have been several days or weeks after having taken the shot. But buried within the image file itself is a special record of the moment that the shutter was pressed. This file 'metadata' does not change when you move the file around between memory cards, hard drives, removable disks, the internet, etc.
The simplest way to find a picture's EXIF date and time is by holding your mouse pointer steady over the file while viewing it as a thumbnail in Windows Explorer (View / Thumbnails). A pop-up will appear with the EXIF date and time clearly visible. Specialised image programs provide access to far more EXIF information as recorded by your camera, such as shutter speed, aperture, flash, etc. I recommend the freeware Irfanview image viewer for its light weight and power.
If your picture dates and times are incorrect, you can use the method below to reset the dates and/or times of your entire pictures collection, or a portion of it, in one go.
You will need to know, for any given batch of pictures, an instance of an incorrect date and time, and for that same instance, what those figures should have been. If nothing else has changed in the meantime, you can work this out from your camera right now: Record what the camera thinks the date and time is, and what you know it should be. If your camera is now broken, lost, sold, or otherwise inaccessible, find a picture in your collection for which you know the date and time (or as close to it as you can get), and use this information together with the incorrect embedded metadata as your rosetta stone.
Armed with your wrong date and right date information, go to this online date calculator and enter the 'wrong' information as the start date and time, and the 'right' information as the end date and time. In the example below, you can see that my camera thought it was inhabiting June, 2007 when in fact the real world was experiencing May, 2008.
Next, download and install the handy freeware EXIF DateChanger 1.1 by Greg Driver.
Run the program, select the source folder for your mis-dated pictures, and then an output folder where the program will create duplicates with re-written DateTime metadata values. The image data is not otherwise changed (so no JPEG degradation etc). The original files in the source folder are not affected at all, meaning that if you make a mistake you can always revert to the originals and try again until you're happy with the results.
The next step is to plug the calculated date and time differential into the appropriate Correct time by fields.
Under the Options tab, check Recurse folders if you need the program to do its magic on subfolders within your chosen source folder, which might well be the case if your photo collection is organised on your hard drive using dated folders, for example.
Optionally, you can even rewrite the filenames themselves to reflect the corrected EXIF date and time. This feature produces accurate and informative filenames as a bonus to the corrected EXIF data. If necessary, experiment with a small group of dummy source files until you have tweaked the generated filenames into a suitable format.
If you've used Photoshop on some of your images and exported them through the Save for web and devices interface, you'll probably find that the above will produce kooky results on the new filenames of those images. Photoshop does something to the metadata that throws EXIF Date Changer off (the latter corrects the EXIF data in the DateTimeOriginal field, but does a double-adjustment on the DateTime field and uses that as the source of the filename). This is nothing to worry about if you haven't edited and re-saved your images in this way.
For simpler operations where you want to apply a single date and time setting to one image or a group of images, you can try EXIF DateChanger 1.0 by Igor Tolmachev (similar name, also freeware, but quite different). This program does not allow a running date offset to be applied to your photos using the constant differential we calculated above. It can apply various dates from the file itself, or a custom date and time that you nominate, but that same information will be applied to the EXIF data in all images selected, regardless of when they were actually shot. This might be useful in certain circumstances.
To avoid having to go through the above hardship in future, it doesn't hurt to keep an eye on your camera's date and time settings. And don't forget to adjust them when travelling.