Please describe the problem:
Localized long date format errors under es language environment
example:
wrong format: 18 diciembre 2008

right format: 18 de diciembre de 2008

Steps to reproduce:
All operations should be done under es_MX(Spanish Mexico) system environment.
steps1:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder with some image files.
4. Pitch on a image file. Make sure the item "Statusbar" in menu "View" - "Show/Hide" is checked.

steps2:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Make sure there are some duplicate images contained localized characters in some folder.
4. Choose the item "Search for Duplicates…" in the menu "Edit". And click button "Search" in the pop-up dialog box.
5. Pitch in a duplicate file.

steps3:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Pitch on a image file whose name is contained localized characters in the files preview frame. Make sure the item "Image Preview" in menu "View" - "Show/Hide" is checked.
5. Click button "Image data" in the "Image preview frame".

steps4:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Pitch on a image file whose name is contained localized characters in the files preview frame. Make sure the item "Image Preview" in menu "View" - "Show/Hide" is checked.
5. Click button "Image comment" in the "Image preview frame". 

steps5:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Right click on an image file and choose "Properties".
5. Click tab "General".

steps6:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Right click on an image file and choose "Properties".
5. Click tab "Comment".

steps7:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Pitch on an image file and click button "Fullscreen" in the tool bar.
5. Click button "Proerties" in the tool bar in full screen mode.

steps8:
1. Login OS using OS user name contained localized characters.
2. Runs "Gthumb Image Viewer" under "Graphics".
3. Go to a folder contained some image files.
4. Double click an image file to preview it.
5. Click button "Proerties" in the tool bar in the "image preview" window.

Actual results:
date format: 18 diciembre 2008

Expected results:
expected date format:18 de diciembre de 2008

Does this happen every time?
yes

Other information: