As we're counting only weekdays, 1000 days is 200 weeks. Once we restore the weekends, that's 1400 days or about 3.83 years. Three years which include one leap year (2016) contain 1096 days, leaving 304 days beyond Jan. 1, 2018. That's about 10 months.

31+28+31+30+31+30+31+31+30+31 = 304 exactly

If we had to add zero days, it would be Jan. 1. But 304 more brings it to Nov. 1, 2018.

The second part, 2015 weekdays after Jan. 1, 2015:

That's 403 weeks or 2821 calendar days or about 7.72 years, including two leap years (2016 and 2020). Seven such years add to 7*365 + 2 = 2557 days, leaving 264 remaining of the 2821. 

31+28+31+30+31+30+31+31 = 243

264 - 243 = 21

The date is Sept 21+1, 2022, i.e., Sept 22.