Start by opening the Registry Editor. Type regedit into the Start menu and launch the utility. Accept the administrator's prompt and you will access the Registry. As usual, be careful when staying here because only one wrong operation can lead to system crashes. 

 

Unlock Advanced with this link:

HKEY_CURRENT_USER Software Microsoft Windows CurrentVersion Explorer Advanced

Right-click on the Advanced folder in the left bar. Select New> DWORD (32-bit Value)and name it.

ShowSecondsInSystemClock

Next, double-click this value in the right panel. In the Value data field , set the value to 1 . Click OK to save the changes, then close the Registry Editor. After logging out and logging back into the account, you will see the number of seconds displayed on the clock.

If you don't want to display the number of seconds, return to the Registry, change the value to 0 or delete it.

I wish you all success!