Browse to the following link, agree to the terms. On the next page, select "Identification type" to be "Client ID Number". Then in "Identification Number", and enter UCI in the format xxxxxxxx (no hyphen). Fill out rest of the details, and you should be able to log in. Then click on "In Process".i don't know when the processing started. I still do not know how to track it. I went to the cic tracking page, and entered the UCI number but it says cannot find applicant. So I gave up on that. and now I got an email.
So unless you have an answer, I would just put the processing date and test interview received date as the same date; ie. 1/10
https://services3.cic.gc.ca/ecas/authenticate.do?app=