Early enough that the subsidiary is demonstrably operating and the continuous year is complete on the filing date, then allow standard processing or premium processing before the season begins.
Count backward from the season, then add the missing year
Hypothetical example: a Frontenac Islands producer wants its manager running the New York yard by the first cutting in June. Working backward, the petition must be filed with the continuous year already completed, so if the only clean year ends in March, filing cannot happen before April. The subsidiary must be doing business at filing, so the yard lease, registrations and first invoices should exist by the winter before.
Standard USCIS processing times vary and premium processing offers a decision within a set number of business days for an additional fee; as a Canadian citizen the manager may alternatively present the petition at a port of entry, where the decision is made at the booth. A realistic plan starts the corporate paperwork a full year ahead, keeps the manager employed through the intervening winter on genuine duties, files in early spring and treats the first season as a test of whether the U.S. operation can support a manager's role at all.
Hypothetical example: A Frontenac Islands wholesale nursery acquires a U.S. distributor that needs a manager before spring shipments begin. The first review should identify the last date on which the Canadian employee has completed the qualifying year and then allow time for the petition record.
Payroll and personnel records settle the qualifying-employment dates. A closing date alone does not establish that the U.S. position, premises, and reporting structure are ready for a managerial transfer.