FitNesse. UserGuide.
TodaysDate [add child]
To diplay todays date:

Markup Text
Displayed as
Today is !today. Today is 05 Oct, 2022.
XML is !today -xml. XML is 2022-10-05T12:52:41.
Right now it is !today -t. Right now it is 05 Oct, 2022 12:52.
Tomorrow is !today +1. Tomorrow is 06 Oct, 2022.
Last week was !today -7. Last week was 28 Sep, 2022.
The month is !today (MMM). The month is Oct.

As you can see, you can add or subtract days. You can include the time tiwh -t. And you can use your own format for the time. (See SimpleDataFormat for the syntax.)