The short answer is no. The long answer is maybe

The clock on the N9 is called a low power mode (or something on the theme). Basically, only the pixels showing the digits are on, the rest of the display is off. It is a feat possible because the N9 uses an OLED display.

Jolla uses an LCD. That is a different technology which does not offer that possibility. It is either all on or all off. In theory one could leave the display on but the backlight off to save power, but I am not sure about the practicality of such a solution. You probably would not be able to read the clock.

There is an amateur project to add a small OLED display to the back of the Jolla. Look it up in this forum if interested. Something like OLED TOH.

EDIT: Here it is.