Most computers do this. Even having auto settings. Check Linux support.

To see whether Firefox is confused about the current date, you could try running the following snippet of code in the web console. Either:

• Windows/Linux: Ctrl+Shift+k
• "3-bar" menu button > Developer > Web Console
• (menu bar) Tools > Web Developer > Web Console

Type or paste this in the line at the bottom and press Enter to execute it:

var d=new Date(); console.log(d.toLocaleString());

That should display the current date/time on your system.

If it's 1969 there, check your system clock. (Or if you run Firefox in a VM or other virtual container, your container's clock.)

If that is correct but printouts are incorrect:

Is the problem in a header or footer? Firefox stores different header/footer field settings for different printers. The &D placeholder should be replaced with the current date and time. Could you check:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste print.*head and pause while the list is filtered

(3) Scan down the list to see whether there are any hard-coded dates

(4) In the search box above the list, type or paste print.*foot and pause while the list is filtered

(5) Scan down the list to see whether there are any hard-coded dates