How do an average for a column type date

NumDays = DATEDIFF(0;IF(TECHNIKE[THCJDATE]>0;TECHNIKE[THCJDATE];0);DAY)

DATE MOY = FORMAT(DATE(2000;1;INT(AVERAGE(TECHNIKE[NumDays])-36523));"YYYY-MM-DD")

Here is the issue...  These values are wrong...  I'm not sure how your 'Date MOY' is being caculated (or where it's from) but 2015-12-08 and 2015-12-06 should only be 2 NUMDays apart, not 230,000+

I try to modify the colum but i have an error and i don't understand why i have this error

Hi AlexGallet01,

What does the error message point to? Could you please translate it to English?

Regards,
Yuliana gu

Hi,

My start date are above my end date

Or it's impossible because my start date are 0

Hi AlexGallet01,

To use DateDiff function, we should meet the syntax that "the start date cannot be greater than end date". Otherwise, it will prompt error.

Regards,
Yuliana Gu