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

Markup Text
Displayed as
Today is !today. Today is 12 Nov, 2026.
XML is !today -xml. XML is 2026-11-12T01:59:05.
Right now it is !today -t. Right now it is 12 Nov, 2026 01:59.
Tomorrow is !today +1. Tomorrow is 13 Nov, 2026.
Last week was !today -7. Last week was 05 Nov, 2026.
The month is !today (MMM). The month is Nov.

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.)