Shading certain dates on time chart + link to calendar

[johnnylzep]

I'd like to have certain periods of the year shaded (as that of High, Low, Peak etc.)- to make it easier to see the seasonality in the data. Is there a way to pick a period each year which will be shaded? I work in two different excel files. The first shows the data linked to the chart and the second shows the seasonality in a calendar. The best for me would be a link between them, so as when I change the dates for High period in the calendar, this change should be shown on the chart. Is that possible? seasonality changes every week!
Chart+seasons.xlsx

[johnnylzep]

I tried and solved the first part of what I want to do and now I have shaded certain periods in my graph. As you can see in the attached file, I just put a secondary vertical axis and I inserted a series for each one of my seasons (High, Low, etc). The problem now is how can I match each of one my dates with those of the calendar and detect each color that assigns to a specific season? For example, I need sthg like that: if(DepDate="CalendarDate in RED color", High, DepDate="CalendarDate in GREEN color", low, etc..)