You have three years to use the week. If the first day of your timeshare week that you deposited is Dec 1, 2018 then you can trade for any date from Dec.1, 2017 (1 year prior to your timeshare week)until Dec.1,2020 (2 years subsequent to your timeshare week). If you deposit within the year, for example April 1, 2018, you do not get any additional time and your trading range would be 2years, 8 months.
So the simple answer, it is based on the date of the timeshare week (i.e.week 46) not on the date of deposit

Hope this makes sense and helps