Dashboard Index, Field filter on relative date

I have a dashboard index widget. In the Field Filters I have a date field.
I want to specify a filter that says “my_date < ‘today’”

I dont know how to format the filter value for ‘today’

I tried CURDATE()
I tried date(“Y-m-D”)

these do not work

When I enter the date specifically (say 2020-5-22), it works

How do I specify a relative date?