| date | entity | event | name |
|---|---|---|---|
| 21/04/1891 | fabergeegg | Year of acquisition | Memory of Azov |
| 21/04/2000 | flag | date Adopted | Flag of Sevastopol |
| 21/04/2020 | operating system | date released | Xbox One system software |
| 21/04/1989 | operating system | date released | Game Boy |
| 21/04/2016 | operating system | date released | Mythbuntu |
| 21/04/1921 | organization | date founded | Eno Center for Transportation |
| 21/04/2004 | organization | date founded | OWASP |
| 21/04/2000 | organization | date founded | Centre des monuments nationaux |
| 21/04/1970 | organization | date founded | Arcata Community Recycling Center |
| 21/04/1997 | animal name | date born | Millenary |