Timing within a month for Upgrading to R12

I have a question on the timing within a month for an upgrade.  If an upgrade from 11.5.10.2 to 12.2.4 is performed mid-month, will there be any issues?

My largest concern is in reference to the subledger tables but could affect other areas also.  The modules used are Receivables, Payables, Inventory, Fixed Assets and Cash Management. I will use an example for an upgrade planned for day 15 of the month, with a 5 day down time.  There will be upgraded transactions within the subledger accounting tables for activity from day 1 thru day 14 that were originally accounted in 11i.  System is down until day 20 when transactions begin in R12.2.4 for day 20 thru day 30. Will this create any issues within the subledger tables to