You may notice that after cycling power to your LS HMI that the internal clock has reset back to 12:00.  You may also notice that your "HK" keep registers are not saving after a power cycle. This occurs because, by default the battery backup is disabled. 

Remove the battery/DIP switch cover on the back of the HMI.  Below you can see the default settings. 

Move the position of switch 1 to the UP (ON) position.