Changing turn numbers and associated dates

[DavoM]

Hi, I am aware of how to change the number of turns in a scenario by editing the respective line in the scenario file (and sticking to the x12 rule i.e. 12 turns - monthly, 24 turns - bi-monthly (15 days), etc.). I also understand that changing the amount of turns in itself does not alter the effects of supply, MC, loyalty rate changes, etc. that remain the same as the originally intended.

Anyway, when I have changed the turn amounts from 12 to 24 for instance, the dates in the scenario no longer match what they were originally/should be. For example - TYW Grand Campaign begins Sep 1618, but change the turns to bi-monthly and it starts in Apr 1618 instead. I have seen other mods that have changed the turn numbers and successfully retained the intended date range. Where and what file do I need to edit for each scenario in order to have the dates remain correct?

TIA!!