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

[LindseyGreidanus]

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?

[jcarlson · Accepted solution]

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

[LindseyGreidanus]

Thank you!

[ChrisUnderwood · Accepted solution]

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