Wrong file display date

[Loxley]

I have a small issue with my gallery (its address is http://car-brochures.c0.pl ).
For a couple of days every time anyone views a file, the date of this display is registered as "Jan 01, 1970 at 01:00 AM" - as seen at the end of the page here:

http://car-brochures.c0.pl/thumbnails.php?album=lasthits&cat=0&page=5

When I upload a new file, the upload date is correct. I have checked the configuration but everything seems to be in order and I don't recall doing anything that might have affected this.
I have no idea what may be the cause of this. It's not a big problem, but if there is some relatively easy fix, I'd like to get it corrected. Any ideas?

[Αndré]

The only way to "fix" this is to view the affected images, so the timestamp gets updated with a valid date.