Ok, I solved the problem.
The solution seems quite simple and stupid at the same time: Your LCID is not the same of the Server.
I've put the Forum according to Portuguese LCID, after talking to the server hosting company - they told me that the server was configured to Portuguese time system. Then came this problem and suddenly I remembered changing the LCID to the UK code, since the GMT is the same as in Portugal. AND IT WORKED!
CONCLUSION: Check very well if the server's hosting company is telling you the truth about the server settings.