I am currently trying to determine my tax status. I am wondering if I should take 2019, 2018, and 2017 or rather 2018, 2017, and 2016 as the year set with which to determine if I am a resident for tax purposes. I was on an F-1 visa from 2013 to 2017, spend a year away from the US, and returned on August 2018 again on a new f-1 visa.
If I have to take 2019 as the current year, which seems more likely given what I saw in the IRS, how many days do we have to count? Is it between January 1st and now, between January 1st and April 15th, or do I have to estimate the days I'll be here for the remaining of the year?