How to calculate inception-to-date retained earnings?

On a custom report, I need to provide:

the retained earnings amount at the beginning of the year

YTD net income/loss

ITD retained earnings

There is no problem with the first 2 amounts.  However, I am struggling with the calculation for the ITD retained earnings.  I can total Period 1 through Period 14 for all the income and expense accounts to calculate the YTD net income/loss.  It matches the total on the simple income statement.  It would seem that the the ITD retained earnings could be calculated by adding the Prior Year Balance Forward to the Period 1 through Period 14 income and expense accounts.  However, it is not calculating the same total as taking the Balance Forward Amount for retained earnings and adding