Question about Strategy and Template Method pattern

so I've been using a strategy pattern together with the template method pattern to create some logic that changes over the years. Let me try to explain:

• My logic is different per Country (EN, PT)
• For each country it's also diff per year but some methods can be the same over the years.

So what I've got in terms of code is:

• common interface "IWork"
• a strategy class that giving the country and year returns the correct country-year class. ex: Work_EN_2018 or Work_PT_2019
• country-year implementations (ex: Work_EN_2018) that extends from a base class (BaseWork_EN)
• base class per country (BaseWork_EN or BaseWork_PT)

It all works good but now with over 10 years things are starting to be hard to maintain all because some methods are the same for multiple years but after a specific year logic changes. So our solution for now is if logic changes for a specific method we change the base class method with the new logic and for all previous years we override the method in the year class (ex: Work_EN_2017, Work_EN_2018, etc). This is very troublesome and hard to maintain so my question is how can this old logic be maintained in a better way?

For now, I'm thinking in creating an utils class with these old methods so that at least in older class years I just reference one single implementation, it's this the only solution?

Sorry if the description of the problem is not clear.

Thanks