Substantial Presence Test -Tax filing 2017, Current Year means 2018 or Tax Year(2017) ?

It is a calculation based off of 2017, 2016 and 2015.  If you were present in the United States for 183 days or more last year (2017, and not under a visa that considers you a nonresident), you pass the Substantial Presence Test.  Otherwise, you will need the following formula:

Add (All Days Present in U.S in 2017) + (All Days Present in U.S. in 2016 divided by 3) + (All Days Present in U.S. in 2015 divided by 6).  If that result is greater than 183, you also pass the substantial presence test.

Example 1:  You came to U.S. on April 1 and remained in U.S all year.  You meet the substantial presence test (greater than 183 days)

Example 2:  You came to U.S on August 1 and remained in U.S. all year.  In addition, you had previously been in the U.S from January until October 31 of 2016.  You meet the substantial presence test (153 days in 2017 and 300/3=100 days in 2016, for a total of 253 days)

Example 3:  You came to U.S. on January 1, 2015 and stayed until March 31, 2016.  You were outside of the U.S until October 15, 2017, and then stayed for the rest of the year.  You would have met the substantial presence test in 2016, but you do not in 2016:  71 days present in 2017+ 91/3 days present in 2016 (total of 30 1/3 days) + 365/6 days present in 2015 (61 days), for a total of 162 days.  Since this is less than 183, it does not meet the test.  For 2016, the calculation was 91 days + 365/3 days, or 122 days=213 days, which meets the test for 2016, but not for 2017