NodeJS testing datetimes with different times of the day and timezone

I have a situation that places today date in DB and I use vanilla code.

const todayCloseDate = new Date().toISOString().slice(0, 10);

This obviously introduces a problem with my timezone (CST) that after 5:00 PM date becomes the next day value. I changed handling to the package data-fns (moments.js is not an option).

const todayCloseDate = DF.format(new Date(), 'yyyy-MM-dd');

It works as expected. My question is how to unit test such change? It would require to make a change in system time of a local machine what locally run tests as well in any testing environment that would run tests in CI/CD pipeline (it would CircleCI, and Jenkins).

Would to start test scenario that would cover such bug and ensure fix? My test runner is Jest.

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