| date | entity | event | name |
|---|---|---|---|
| 11/09/1985 | eruption | date | Armero tragedy |
| 11/09/2012 | file format | date released | Opus (audio format) |
| 11/09/1964 | protected area | date founded | Fire Island National Seashore |
| 11/09/2009 | organization | date founded | ADS Group |
| 11/09/1962 | organization | date founded | Kasturba Health Society |