How can we close our current company (year end) mid month, and open as new company?

My company is being acquired, and we will at some (currently undetermined time) need to close our GL books as the current company, and open as the new company.  This will probably happen mid month (we have no control of when that happens). which will also be mid year.

Can we simply process a year end and continue on?  what happens to the remining days in the current month, or do we need to do something special to our calendar?

I'm looking to see if anyone has experiencing in this and if you have any recommendations or documentaion you can refer us to.