Date variable to number day year

[tjeerdhage 5]

I have a date variable 12-10-2021

I want to change it to the day number (286)

 

What lua script do I need. 
I thought it was easy with stringformat and getvariable, but that gifs a error. 
 

[10der 832]

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if i not right catch your question - another way ? 

 

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286 day of 2021 y

[jgab 2,645]

...it becomes 285 for me...

 

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