HP Probook 450 G4 laptop doesn't boot up, gives POST error after hard reset

[sup91]

Product name: Probook 450 G4

Product number: W7CB9AV

My laptop doesn't boot up when I press the power button. Even the HP logo screen doesn't come up and fans don't start either. Sometimes power button light and caps lock key light come up but still doesn't boot.

Sometimes when I do hard reset (press and hold power button for ~15 sec) next the laptop boots up but gives a POST error code 005. And sometimes after getting it to boot up and working in windows, it restarts again automatically and gives the same error.

The system time is invalid. This may be a result if a loss in battery power.

Set the correct time and date using your operating system. If this message perists,

you may need to replace the onboard battery.

Real-Time Clock Powerloss (005)

 

POST error after hard reset

[mdklassen]

The system time is invalid. This may be a result if a loss in battery power.

Set the correct time and date using your operating system. If this message perists,

you may need to replace the onboard battery.

In Windows, what happens if you click the "clock" at the bottom-right of the screen, and then manually change the date & time & timezone settings?