They are called the Trinity Trio. The date might differ to be a few days before or after though because March 28 is already the major day and anniversary of when the games started. Sora is also the only character's birthday that ever has been canonically confirmed and it's on that way.

𝕾𝖔𝖒𝖊𝖙𝖍𝖎𝖓𝖌'𝖘 𝖜𝖆𝖎𝖙𝖎𝖓𝖌 𝖙𝖔 𝖕𝖔𝖚𝖓𝖈𝖊, 𝕽𝖊𝖉 '𝖓' 𝖇𝖑𝖆𝖈𝖐, 𝖆𝖓𝖉 𝖘𝖑𝖎𝖒𝖞 𝖌𝖗𝖊𝖊𝖓 𝕬𝖗𝖊𝖓'𝖙 𝖞𝖔𝖚 𝖘𝖈𝖆𝖗𝖊𝖉? ₊ ⊹ . ݁˖ . ݁⋆ ˚｡⋆⊹ . ݁˖ .

Making Kingdom Hearts Stuff Until KH4 Comes Out (Day 169)

Donald, Goofy, and Jiminy's reunion with King Mickey as Sora and Lean watch on.

Ansem the SOD is referenced, but the King was actually referring to Ansem the Wise.

Technically, Ansem the SOD is not an impostor. He is heartless of Apprentice Nort. In turn, Old Nort had taken possession of Terra’s body and impersonated Ansem the Wise's name.