If I understand you correctly, that's what the period offset in the intital setup is for. Let's say you have a 4-second cycle. As you say, sines usually start from the center - your ABC analogy will go like this:
B(0 seconds), C(1 second), B (2 seconds), A (3 seconds), back to B (completes the 4th second/back to 0)
Therefore if you set the period offset to 3, you begin at A. Setting the offset to be exactly 75% (or three quarters) of the cycle duration will give the effect you want.