Extends d as xojo.Core.Date

I want to extend the xojo.Core.Date class with a function,
but compiling gives error The extends modifier cannot be used on a class method.

Whats wrong?

[quote=174265:@Jaap Cammeraat]I want to extend the xojo.Core.Date class with a function,
but compiling gives error The extends modifier cannot be used on a class method.

Whats wrong?[/quote]

Your method should be in a module.

Thx!