EVN — Event Type
Appears immediately after MSH in ADT messages and other event-driven message types.
The EVN segment provides additional event information for ADT and other trigger event messages. It records when the event was recorded versus when it actually occurred, and who initiated the event.
Real-World Context
EVN is critical for audit and reconciliation. The difference between EVN.2 (recorded datetime) and EVN.6 (event occurred datetime) can reveal data entry lags or backdated entries. When investigating discrepancies in patient timelines, always compare these two timestamps to understand the documentation lag.
Field Reference
Click any row to see the full description, common values, and troubleshooting tip.
| # | Field Name | Type | Req | Max Len | |
|---|---|---|---|---|---|
| 1 | Event Type Code | ID | O | 3 | ▶ |
| 2 | Recorded Date/Time | TS | R | 26 | ▶ |
| 3 | Date/Time Planned Event | TS | O | 26 | ▶ |
| 4 | Event Reason Code | IS | O | 3 | ▶ |
| 5 | Operator ID | XCN | O | 250 | ▶ |
| 6 | Event Occurred | TS | O | 26 | ▶ |
| 7 | Event Facility | HD | O | 241 | ▶ |
Example Segment
1EVN||A01|20260310143205||01|1234^SMITH^JANE^^^RN|20260310140000
Related Segments
Used In Message Types
Parse messages with EVN in real time
Paste any HL7 message into our free viewer. Decodes every segment and field instantly, client-side.
Open HL7 Message Viewer →Need HL7 mapping templates?
The HL7 Integration Toolkit includes field mapping worksheets, interface spec templates, and a go-live checklist for every major HL7 message type.
View HL7 Integration Toolkit →