Global undocumented function setYear appeared in 5.1.
In 5.0, there was so function called setYear:
Lucee 22.214.171.124-SNAPSHOT Error (expression)
Message No matching function [SETYEAR] found
In 5.1, there is a globally available, and undocumented as far as I can tell, function called setYear:
Lucee 126.96.36.199 Error (template)
Message too few attributes in function [setYear]
Pattern setyear(date:datetime, year:number [, timezone:timezone]):datetime
This breaks existing applications that define their own setYear function.