Different Time zone with Auto Conversion for Pending Worker

We're using Auto Conversion for Pending Worker for a while.
There's some questions need to be clear.
As we know, If the Pending Worker's hire date is 2025.01.01
When the day is come, the Pending Worker should be hired, and transfer from Pending Workers to Employee at 00:00, 2025.01.01.

But in our case, the Pending worker did't auto convert by the time. It might be convert on 09:00, 12:00, 16:00 or 20:00.
We have no idea how to get the time.

Our Legal Employers are base by 5 different country.
The HR who add pending Worker might from different Legal Entity for the Pending Workers. (Different Time Zone)