Date and other infos inside the pictures dissapeared

[stankovic]

I noticed that in many of my pictures some important information inse exif tags have dissapeared - mainly the date when picture was taken. Does somebody of you know how that could happen? I've never removed the info with intent. Apart from xnview, i tested picasa and microsofts photoviewer. Can it be that windows 7 and its explorer is responsible for that?

Edit:
Forgot to mention that i also tested adobe lightroom

[helmut]

Hmm, sounds strange. Did you edit and save the pictures? Did you save the pictures in a format other than JPEG?

[stankovic]

No, i didn't! They are the same JPG-files i copied from camera to the disc. I can't say what the tools, i've tested so far, did with these pictures. The damage is minimal because i have a backup but nevertheless i would avoid that for the future. I looked into more details of these images and there is one conspicous detail: the modification date/time is the same (01.01.2007) and that same date is before the pictures was taken!

[xnview]

Do you remember which feature was used on your pictures?

[stankovic]

(Sorry for not answering a long time)

I think i tested Picasa extensively: f.e. the collage feature and so on. But i can't remember to have saved an edit of a picture. To be fair: as long as Picasa is not known for doing such weird things i want claim that program just because i used it for some time.