820 ILCS 154/15
An employee who is entitled to take paid or unpaid leave (including family, medical, sick, annual, personal, or similar leave) from employment, pursuant to federal, State, or local law, a collective bargaining agreement, or an employment benefits program or plan may elect to substitute any period of such leave for an equivalent period of leave provided under Section 10.
(Source: P.A. 99-703, eff. 7-29-16.)