14 Ill. Adm. Code 510.60
Computation of Time
Section 510
Section 510.60 Computation
of Time
Computation of any period of
time prescribed by this Part shall begin with the first business day following
the day on which the act, event or development initiating that period of time
occurs, and shall run until the end of the last day or the next business day if
the last day is a Saturday, Sunday or federal or State holiday. Timeliness
shall be deemed by the date of postmark, the date of hand delivery, or the date
received electronically by the designated email address.