Yes, the stories on Dateline are usually based on real events and facts.
Dateline is known for delivering true stories. However, sometimes for dramatic effect or to make the story more understandable, there might be some minor adjustments or reenactments, but the core of the story remains true to the actual events.
Most of the time, Dateline presents true stories. They do extensive research and verification to ensure the accuracy of the information they report.