Site: nolo.com
... for leave under USERRA, the employee must meet certain requirements, including:
giving the employer notice ... Employees must give 90 days' notice of training dates.
Illinois
20 Ill. Comp. Stat. Ann. ... If reasonably possible, employees must give advance notice of military service. ... Employees must give as much notice as possible of their need for this leave. ... Employees must give advance notice of service. ...