Conversation so far:
Is there anything interesting on Girl's Generation?
One of the prominent figures of the Korean Wave, Girls' Generation has won numerous accolades and the honorific nickname The Nation's Girl Group in their home country.
What was Girls' Generation's Lion Heart?
Lion Heart is the fifth Korean language studio album recorded by Girls' Generation.
Was Girls' Generation's Lion Heart a successful album?
Girl's Generation's Lion Heart experienced commercial acclaim in South Korea, staying atop the Gaon Album Chart for two weeks and becoming the 13th best-selling album of 2015 .
Who made Girls' Generation's Lion Heart album?
Lee Soo-man produced Girls' Generation's Lion Heart.

Question: when did lion heart come out, what year?
Self-contained rewrite: When did Girls' Generation's Lion Heart come out, what year?