I don't know any airline which will accept checked luggage the day prior to departure. That is why most airports have storage facilities. I used the one in T1 at YYZ yesterday (3rd level, in the travel store before security) and it works well. $4 CAD for a small bag, and $6 for a big one. Plus GST of course!

I also checked out the arrangements at SYD. The storage cost is much higher ($20 AUS/day). We decided to bring our checked luggage into the city and found the Airport Link staff were very accommodating! Yea, Sydney public transit! I can't wait till YYZ has a direct airport link!