Data lookup in sinusoid function

Hello, I have an excel question I've been puzzling on the last few days:

I have values that I have scatter plotted into a chart and gave a sinusoid function.
The y-axis has values ranging from -10000 to 10000, and the X-axis is time in hours.
The thing is, I want to calculate the time difference between two peaks of my chart. This can be estimated from the figure, but I want the exact data.

What I've done so far:
I've estimated in which range of cells the peak is (y-value) and looked this up with the Max function. Example: Max(H111:H237). This gives me a value. I want to know which cell corresponds with this value.
Somehow Ctrl+F doesn't help me find this value, so I have to search for it manually in the column, so I can see which cell from the X-axis corresponds with it.
This all is quite cumbersome, and I just know there is a function for this in excel. The lookup function hasn't helped either, because the data needs to be in ascending order for that to work.

Thanks for the help in advance!

Did you try VLOOKUP? The data doesn't need to be in any specific order.

How noisy is the data?

You need:

=INDEX(R111:R237,MATCH(MAX(S111:S237),S111:S237,0))

because your lookup column is to the right of the resultant column so basic VLOOKUP can't be used....

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