After hours of reseraching I could not clear a date value on the SharePoint list using Powerapps. I got this to work by using flow. However, it's not what I wanted to use for something as simple as this, but it was a workaround for now incase anyone is looking for one.
Create new Instant Flow, initiated by PowerApps button.
Get Item, 'ask in powerapps' for the ID. In PowerApps on a button I did... On Select: FlowName.Run(ThisItem.ID)
See screenshot for steps in flow. In the date column, I went to the Expression tab, typed in null and clicked OK. Inserts a Null expression.