Dynamic Shading Value?

Questions
#1

Is there any way to update the shading value by date?

For around 8-9 months of the year my shading is 0. However for about 6-7 weeks either side of the shortest day (22 June here in NZ) I get shading (From a single Totara tree in the paddock next to my panels) till around mid-day. e.g.

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is there a handy script anywhere to dynamically update the shading value based on date?

#2

Its a fixed value that applies to the whole day in the estimation.

#3

Yes it’s fixed… But I’d like to make it dynamic on mine because it varies based on the time of year.