Hi there! Just tagging @jwilliams79, @rstambolieva, @berat can, and @Laure.vanpelt for some potential help!
Hi @AnnaCzarnik,
Here some insights that might help 
- The vacation balance is not calculated based on the employee’s status but on the accrual policy you assign. If the yearly entitlement changes, you’d have to update the accrual policy but as far as I’m aware this change can only be implemented “from hire date” or “from current entitlement period”. So if your entitlement period goes from January to December, it would update it retrospectively. The easiest would be to adjust the entitlement manually for this year and then assign the new accrual policy as of the next entitlement period.
At least that’s how I see it. Maybe someone has more insights and knowledge about this. 
- Yes, I’d just update the existing profile and schedule the changes to the respective date when the change happens
- I would have said yes as it’s tied to the profile but can’t say for sure as we don’t use the P&D section at our company.
I hope that helps? 
Hi you all,
Thank you for your already given input! @SabbuSchreibers points cover the most important elements already. :)
@AnnaCzarnik I’d like to add some notes. We (somewhat) recently released the first iterations of a re-hiring functionality, that make the re-hiring approach for employees way easier. We plan on expanding here as well. You can find some more information here. As @SabbuSchreiber already mentioned, you can easily schedule the respective data changes. For that however, we urgently advise that the attribute >hire date< is not touched for the new employment! Changing the hire date has the potential to distort the employee data history.
So basically, if you feel like you want to start a kind of new employment that will have it’s own start date and requires an own hire date, independently from the former employment, using the re-hiring functionality and creating a new profile might be the better approach. If you won’t touch the hire date, Sabbus comment is the way to go. :)
All the best
Michael