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Power Platform Community / Forums / Power Automate - Building Flows / Explanation convert Da...
Power Automate - Building Flows
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Explanation convert Date from Excel in Iso Format

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Posted on by HansenvomDeich 182

Hello,
I also always try to understand the things that I use by searching and then copy-pasting.

The following constellation:
Excel date in Cell:
25.01.2023
Input into Power Automate:
44951

 

Expression for converting and get the correct date without errors in Power Automate:
addDays('01/01/1900',sub(int(outputs('Compose')),2),'dd/MM/yyyy')

I had Chat GPT explain the formula to me in order to improve it for next time.

Why do 2 days have to be deducted? I suspect it's a "simple" computer language that I don't understand yet.

I would be happy if someone could explain it to me.
Thank You

  • Verified answer
    HansenvomDeich Profile Picture
    HansenvomDeich 182 on at
    Re: Explanation convert Date from Excel in Iso Format

    Oh wow, great 😄

    Thanks !

  • Verified answer
    JonDoesFlow Profile Picture
    JonDoesFlow 1,304 on at
    Re: Explanation convert Date from Excel in Iso Format

    Excel's got this funky way of marking the calendar's start line at "Day 0", which it thinks is January 0, 1900. But in reality, Day 1 is actually January 1, 1900. So, when you're trying to match dates from Excel's serial numbers to real dates, you're always a day ahead from the start.

     

    Plus, Excel treats 1900 as a leap year, it wasn't. Thisthrows in an extra day if you're counting dates from way back then. So, between starting the count at "Day 0" and pretending 1900 is a leap year, Excel's date maths can get a bit skewed.

     



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