Based on the Mother Jones criteria for what
constitutes a mass shooting.
To learn more click here.

The term mass shooting is used generically.
Weapons other than guns were used in some mass shootings.

No time zone conversion is used for time calculations and the count up timer application uses Greenwich Mean Time (GMT-05:00) – Eastern Time (United States & Canada). Your time zone, the time of the mass shootings, and other factors like daylight savings time, may produce (in the United States) very slight time discrepancies.