Try asking Siri this (but substitute in your business of choice):

How late is Harris Teeter open?

This works well, though Siri can’t find the hours for some smaller businesses. I suspect this happens when the business does not have a web presence for Siri’s team to scrape.

Note that in the case above (Harris Teeter is open 24/7), Siri replies:

Harris Teeter is open all day today.

Good to know. Read the linked article for more details.