Answer:
Sunday
Explanation:
January 21st, 2015 was a Wednesday, and there are 31 days in January. This means that January has 31 - 21 = 10 days left in the month after January 21st.
Since 10 is equivalent to 3 weeks and 1 day, February 1st, 2015 would be a Sunday (3 days after Wednesday), and February 8th, 2015 would be a Sunday as well, because it is exactly one week after February 1st.
Therefore, February 8th, 2015 was a Sunday.