The hiring period begins as soon as a job is offered to the successful candidate. It occurs at the end of the recruitment process once the ideal applicant for the vacant position has been decided upon. The hiring manager will then make a job offer, and that’s when the hiring period begins.
The hiring period continues through the candidate accepting the job offer, any negotiations that may occur, and through to when they start the job and begin adjusting to the role and work environment. So, rather than ending on their first day in the job, the hiring period continues until the recruit has settled into their new position.