Ah yes… it took me a long time to figure this one out…
You actually need to pass in a string that contains date, time and time zone!
I figured this out by creating a flow variable for the output the widget creates by filling in the text field in flow variables tab:
For test purposes I created two string variables, one with and one without timezone:
When using the one w/o timezone I get the same error as you:
When passing in the variable with timezone it works:
Here is a demo:
flowvartodtwidget.knwf (72.7 KB)
So you pretty much have to add a timezone via string manipulation to make it work!