XFCE4 is my desktop environment of choice in every Linux distro I use these days. However my display resolution of 1366 x 768 on the laptop is quite low by today's standards, so I set the panel (the taskbar) to the left edge of the screen. It looks similar to Unity's bar in Ubuntu. But now I faced a strange issue: while the panel was vertical, the clock was also displayed with a vertical text orientation. Here is a way to make it horizontal.
To set the panel to the vertical orientation, I opened the panel preferences and changed its parameter General\Mode from "horizontal" to "vertical":
After playing for a few minutes with XFCE4's settings editor and config files without any luck, I returned to the panel preferences and decided to try yet another mode of the panel, called the "Deskbar". Once I set it, the clock orientation was set to horizontal automatically.
I hope this article save your time if some day you decide to use the same settings for XFCE4.