The article discusses the importance of the No transactions will be allowed prior to this date option on the Common | Maintenance | Company Details | Accounting Periods screen.

Consider the following scenario to discuss further:
Users may notice that several / a significant number of General Ledger transactions’ dates have all been unexpectedly changed to a specific date.
These incorrect dates can be viewed on, among others, the Account Transactions report and the General Ledger Enquiries screen.
In this case, a majority of transactions have all unexpectedly been changed to 28 Feb 2020

The following steps explain how this issue can be recreated:
1. On the Common | Maintenance | Company Details | Accounting Periods screen, the following date value was initially specified on the No Transactions will be allowed prior to this date field: 28/02/2019
2. Several transactions were processed in the company that commenced on 1 March 2019.
3. Sometime later, the date below was changed to 28/02/2020

4. However, the newly selected date is on or after already/currently processed transactions in the same company. In this case, transactions with dates ranging from 1 March 2019 to, e.g. 28/02/2020
5. When either:
the transaction dates of all GL account transactions processed before Step 3 will be automatically changed to the above date: 28/02/2020
6. The only way to resolve this matter is to either
CONCLUSION:
NEVER change the date value in the above No Transactions will be allowed prior to this date field, to any value after already processed transactions' dates in your company.
It's also recommended to restrict all agents from accessing this screen, except for the main financial manager (e.g. Chief Financial Officer), and other responsible agents.