The documentation page for TONOW() states it

Calculates the number of days between the current date and another date.

although it also shows an example response as

=> 25 days

I believe the help page should be modified to state explicitly that TONOW() returns a descriptive string ('2 days', 'a month', etc.).

Also, TONOW({Yesterday}), where {Yesterday} equals, um, yesterday, returns '2 days' rather than the more expected '1 day'. If '2 days' is the desired behavior, the documentation should probably reflect this.