How can find out when the maxium three day gain (C-C3)/C3*100 took place in the last 30 days using SinceTrue and Max?

I cannot think of a way to do this using SinceTrue().

IIF(C / C3 = MAX(C / C3, 30), 0, IIF(C1 / C4 = MAX(C / C3, 30), 1, IIF(C2 / C5 = MAX(C / C3, 30), 2, IIF(C3 / C6 = MAX(C / C3, 30), 3, IIF(C4 / C7 = MAX(C / C3, 30), 4, IIF(C5 / C8 = MAX(C / C3, 30), 5, IIF(C6 / C9 = MAX(C / C3, 30), 6, IIF(C7 / C10 = MAX(C / C3, 30), 7, IIF(C8 / C11 = MAX(C / C3, 30), 8, IIF(C9 / C12 = MAX(C / C3, 30), 9, IIF(C10 / C13 = MAX(C / C3, 30), 10, IIF(C11 / C14 = MAX(C / C3, 30), 11, IIF(C12 / C15 = MAX(C / C3, 30), 12, IIF(C13 / C16 = MAX(C / C3, 30), 13, IIF(C14 / C17 = MAX(C / C3, 30), 14, IIF(C15 / C18 = MAX(C / C3, 30), 15, IIF(C16 / C19 = MAX(C / C3, 30), 16, IIF(C17 / C20 = MAX(C / C3, 30), 17, IIF(C18 / C21 = MAX(C / C3, 30), 18, IIF(C19 / C22 = MAX(C / C3, 30), 19, IIF(C20 / C23 = MAX(C / C3, 30), 20, IIF(C21 / C24 = MAX(C / C3, 30), 21, IIF(C22 / C25 = MAX(C / C3, 30), 22, IIF(C23 / C26 = MAX(C / C3, 30), 23, IIF(C24 / C27 = MAX(C / C3, 30), 24, IIF(C25 / C28 = MAX(C / C3, 30), 25, IIF(C26 / C29 = MAX(C / C3, 30), 26, IIF(C27 / C30 = MAX(C / C3, 30), 27, IIF(C28 / C31 = MAX(C / C3, 30), 28, 29)))))))))))))))))))))))))))))