Seasonality matters in two places: it can create gaps in the continuous qualifying year, and it determines when the company can spare the person. Both need to be on the calendar before a filing date is chosen.
Map the season against the qualifying window
Draw the three years before the intended filing on a timeline and mark every period the transferee was actually on the qualifying employer's payroll. A processing operation that shuts for part of the year may have kept the manager on salary throughout, in which case there is no issue, or may have laid the role off, in which case the continuous year needs to be located elsewhere in the window or the filing date reconsidered. Separately, the company has to decide when it can release the person, and the honest answer is often the end of a season rather than the start of a fiscal year. A new-office approval runs for one year, which sets the clock for demonstrating that the role has become managerial in substance, so starting at a point when the person can genuinely build the operation matters more than starting early.
Hypothetical example: A theatre-equipment manufacturer plans to move its production manager after its American subsidiary signs a new venue contract, but the foreign payroll system closes monthly. The first review should map the twelve qualifying months against actual pay dates, leave periods, and the planned transfer date. Payroll history settles continuity more reliably than memory. Allow time for entity records, translations, and an organization chart based on current staffing rather than future hiring hopes. A manager cannot begin the new assignment before appropriate permission is in place. Work backward from the intended start, then test whether the future staffing plan makes the proposed role managerial on day one or only later.