# How is a seasonality chart calculated for a specific stock?

I have seen several websites offer a Seasonality chart for stocks, and I tried to recreate it, but my results have the general line pattern, but its not the same as what I see on other sites.

My calculation was as follows:

• Get the Closing price of the stock for each day since the IPO,
• Break down the price to annual results - basically arrays for the closing price per day for that year,
• Create another set of arrays, for each year, where the rate of change is calculated (today's closing minus yesterday's closing), and the first trading day of the year is zero,
• Create another set of arrays, for each year, where it calculates the percent change for each day, (today's closing minus yesterday's closing) divided by today's closing multiplied by 100 to get the percent,
• Then for each year, create a running cumulative percent change; add the percent change for each.
• Create a daily average of the running cumulative change, and then plot it.

Issue is that when I compare my result to what other sites are showing, its different. Is my calculation method correct?