Wizards announced the purchase of TSR, the cash-strapped makers of Dungeons & Dragons on April 10, 1997. Wizards acquired TSR and Five Rings Publishing Group for $25 million. Many of the creative and professional staff of TSR relocated from Wisconsin to the Renton area. Wizards used TSR as a brand name for a while, then retired it, allowing the TSR trademarks to expire. Between 1997 and 1999, the company spun off several well-loved but poorly selling campaign settings (including Planescape, Dark Sun and Spelljammer) to fan groups, focusing business primarily on the more profitable Greyhawk and Forgotten Realms lines.

When did wizards of the coast buy d&d? Okie... think carefully first, then make a decision:
The relevant sentence in the passage is: Wizards announced the purchase of TSR, the cash-strapped makers of Dungeons & Dragons on April 10, 1997. So, the answer is April 10 , 1997.