I have received word from so many people that the 70% off clearance has in fact started at their Target store today. However, it sounds like the Target’s system went down (nationwide) early this morning and the scanners quit working, so some places weren’t able to finish (or even start) the scanning. The scanners are back up and running now, so hopefully you will find the markdown at your store.
It also sounds like many stores do not have the toys consolidated to one aisle, so you may have to do some looking around.
Keep in mind that clearance can vary by location, so there is chance that the markdown has not taken place at your store. You can https://www.facebook.com/allthingstarget/posts/567127076680783 for updates throughout the day on the different location.