Always the weekend before and after Thanksgiving. Then the Muzzleoader season is the weekend after the 2nd weekend. So looking at the calender.......

1st firearm season Nov.21-23
2nd firearm season Dec. 4-7
Muzzleloader season should then be Dec 12-14.......if I counted the days right. I see you wrote "over there". Just beware the out of state fees for Illinois firearm seasons are very pricey $$$. Ican't tell you what they are but Google "Illinois Dept. of Natural Resources" and they should have a list of fees.