If you are looking for an example of how a takeover should be done then look at British Airways buying out of Cityflyer.
If you are looking at how a takeover should not be done then look at KLM's buying out of KLMuk.
The difference is that the former was a UK company taking over a UK company.
For info, the Cityflyer pilots, quite naturally, did not carry over their Date of Joining to British Airways. I don't believe the KLMuk pilots expect, or even have any plans to try, to carry over their Date of Joining.