DiffDate() and Today () not working as expected in Dashboards

Question

I am trying to get a simple count of days till the end of the year and for some reason Arcade is not preforming calculations with Today() like I am expecting.

When I use the code :

DateDiff(date(2025,1,1), date(2024,8,26), 'days' ) -> I get 128 days But when I use the code:  DateDiff(date(2025,1,1), date(today()), 'days' ) -> I get 159 days I am using the advanced formatting window on an indicator in a dashboard. Is there something obvious I am missing here? Why would the today() function add 30 extra days?

today.JPG

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jcarlson · Accepted Answer

In the function Date, the second parameter is the month number, but it's zero-indexed. Meaning 0 = January, etc. So 8 is September.

ChrisUnderwood · Accepted Answer

You might also be able to utilise the ISOMonth function which offers "Values range from 1-12 where January is 1 and December is 12."

https://developers.arcgis.com/arcade/function-reference/date_functions/#isomonth