In the meantime, I figured out that it is locale issue, and I am just wondering is there some relatively quick solution, without the need to check what locales are installed on a server.
On the server I have control of it is ok, but now is an issue on the server I do not have control of.
I know the easiest thing would be to turn of strftime and output as ‘d.m.Y’, in this case strftime is used for nothing special. But I have/had intent to use for something special.
Problem solved.
It is a reminder to always triple check stupid things first, and make sure they are ok.
The client’s config was set to config.website.com.php and he checked www.website.com all the time.
In addition, he didn’t set non-www to www redirect and sent me website.com. From my point, everything looked ok, but he constantly sent me screenshots with faulted dates with %. Which puzzled me.
Until I figured it out.
At least, maybe this thread help someone with the same issue. Thanks!