Windows assumes computer clocks are local time. It can be configured to assume UTC. Other operating systems assume computer clocks are UTC. Many log tools are not time zone aware.

Computer clock is just counter, if you set the start counting point to UTC, then it's UTC, you set it to local time, then it's local time.

that's the difference between "aware" and "naive" timestamps. Python has a section explaining it in their docs (though the concept applies to any language):

https://docs.python.org/3/library/datetime.html#aware-and-na...

AKA time zones