Good to see you back!
This is a simple one - So your column in the table is type ‘Datetime’ and it needs to be type ‘Interval’. Intervals are chunks of time, versus datetimes which are representations of a single time on an actual day. When you take one date (say yesterday at noon) and look at distance to another time (right now), you will get an interval (17 hours).
You can’t change the column type of a table column after it is created, but you can delete the datetime column you created and recreate it as a interval.
Does this make sense?