Hello
Starting to use Manager and need to create all transaction from 1/1/2018 not from now on.
What should I do to ensure all entries/ transaction ( cash transactions, sales, purchasing, inventory, …etc) have correct date and history.
I will use desktop Edition then will upgrade to Cloud.
There is no method for the software to ensure you enter transactions correctly. That is a separate management/review/audit function. After all, it does not know what you do not tell it.
The normal procedure is not to enter transactions from before you used Manager. Instead, you enter starting balances from your previous accounting system. See the Guide: Manager Cloud. The exceptions are unpaid invoices, as the Guide explains.
I am not sure I understand your question. If you are asking how to change a transaction date, you simply type a new date into the Date box on the Edit screen for that transaction.