On old cameras or scanned in photos the incorrect date or no date is set. You can change the date timestamp on the photo if you wish. There are 2 ways. The first way is more convenient if you want to set a few images into different dates. The second way is faster if you wish to set a group of images to the same date.

Changing Date & Time Stamp on images with different dates:

Select the thumbnails of the image or images you wish to have the same date.
Open up the Properties Pane (View | Properties)
Select the Date/Time: checked box and then click on each element in the date (month, day, year, etc.) and switch each element to your desired date.
Repeat for other images. I would suggest working in a folder and do all images that you want to do then go on to the next step.
Select all the images that you changed the dates for.
Choose Tools | Batch Adjust Time Stamp
Choose EXIF date/time original and choose Next
n the New time stamp box: Choose Use different date and time .
In the Select date and time: box: Choose ACD database date and time
Choose Adjust Time Stamp
Choose Done
Changing Date & Time Stamp on images that you want to have same date:

Select all the images that you changed the dates for.
Choose Tools | Batch Adjust Time Stamp
Choose EXIF date/time original and choose Next
In the New time stamp box: Choose Use specific date and time.
In the Select the specific date and time: box: Enter in the appropriate date.
Choose Adjust Time Stamp
Choose Done
To view the dates you have set:

The file will now contain the specified date in the EXIF information of the photo. The EXIF information is part of the file that contains information specifics about the photo