Should be
year-from-dateTime('[%BeginOfCurrentYear%] + [%YearLength%]')
(mind the quotes) See the XPath documentation at world.mendix.com
OK, thank you, this solved my immediate problem.
This seemed to solve my immediate problem. Thank you for that, but then, testing, I figured out that I had to add two years, so I wrote: '[%BeginOfCurrentYear%] + [%YearLength%] + [%YearLength%]'
Then it says: Multiplier in token expression must be an Integer. Any ideas?