Myrtle, Sven, and Muffie each owned a one-third interest in the capital and profits of their calendar year partnership. On Sept. 18, Year 1, Myrtle and Sven sold their partnership interests to Bubba and immediately withdrew from all participation in the partnership. On Feb. 15th, Year 2, Myrtle and Sven received full payment from Bubba for the sale of their partnership interests. For tax purposes, when did the partnership terminate?