Table transpose problem

I'm working with a table that has profit centers as columns and P&L accounts as rows. Here's a simplified sample data:

I'm trying to transpose this table and unpivot the columns so that the data would look like this:

But the problem is the date column which I have to transpose into a row first. Then I have separate account columns for each month which is indicated within the month row but this doesn't really help me. Any ideas how this could be done?

I could transpose the table in Excel first and add the date coulmn afterwards but this isn't ideal as the accounts are different between months.