Always be vague. Say I think they’re in today or not until later. If they press say it’s company policy not to give out the schedule. Most companies do have this and even if they don’t how would a stranger know. Don’t give out specifics, they can get people injured or even killed.
At my last job someone came up and asked when “Sarah” was working next. I didn’t tell him and then texted her a description, turns out he was an abusive ex who had been stalking her. Don’t do this shit please.