Prudent automatically stores the date of the latest available transaction when you import transactions.
Here's an example of what to expect:
While importing transactions
Typically, you click on the "Choose an account to apply to all transactions (debit)" to specify the account to which all of the transactions will be debited to (i.e. if you're importing a bank statement, you choose the bank's account):
When this is confirmed, Prudent automatically records the date of the latest transaction in the list above to provide an indication of the latest date in which transactions in the account is reconciled (i.e. imported from account sources).
While viewing accounts
The latest reconciliation date for an account will be shown in an account list: