column validation <=today throws error with now() as default

Kia ora,

I hope I found the correct forum...

As a recent newbie to PowerApps I wanted to stretch my wings and use a Sharepoint connector to save user collected data into a list.

Creating this list proved tricky.

The scenario is that a field team will mark specific time points and those will be written back to the list for later evaluation (like arrived at point a, finished doing this, etc...), all columns are set to "date and time"

For validation I wanted to restrict the list columns to date/time <=today().

In the column validation field I have:

=[column name] <=TODAY()

first confusion: after saving sharepoint changes this to &lt;= but I guess it should work nebertheless

second confusion: the first column in the set of times has a default value of "today's date", which when I try to add a line to the list correctly generates today's date and the current time. Trying to save this line throws a data validation error at me.

Where is my mistake here?

Thanks in advance for time and help

Hansjoerg