35 Ill. Adm. Code 166.225
Computation of Time
Section 166
Section 166.225 Computation
of Time
Computation of time shall begin
with the first business day following the day on which the act, event or
development initiating such period of time occurs. Time shall run until the
end of the last day or the next following business day if the last day is
Saturday, Sunday or legal holiday. Where the period of time is five days or
less, Saturdays, Sundays and legal holidays shall always be excluded in the
computation of time.