HL7 v2 Reference

HL7 v2 RXA-3 (Date/Time Start of Administration): Format, Values, and Testing Notes

Jul 27, 2026 · 4 min read

RXA-3 is the timestamp that anchors the whole administration event. Get the precision or timezone wrong and a dose can land on the wrong day in a registry, or worse, get treated as a duplicate of a real one.

Quick answer

RXA-3 holds the date and time the administration started, in HL7 TS format (YYYYMMDDHHMMSS, with optional timezone offset). Most immunization and pharmacy feeds send it to at least minute precision; registries commonly accept date-only for historical doses but expect full precision for same-day administrations.

What this field contains

YYYYMMDD

Date-only precision — common for historical or externally-sourced doses where the exact time was never captured

YYYYMMDDHHMM

Minute precision — typical for real-time administration events entered at the point of care

YYYYMMDDHHMMSS+/-ZZZZ

Full precision with offset — needed when the receiving system reconciles events across time zones or against other timestamped segments

Example

Synthetic example Generated by Synthibase

RXA|0|1|20260726090000||08^Hep B, adult^CVX|0.5|mL^^UCUM|||||||||||CP|A

RXA-3 shows a full-precision timestamp (20260726090000) for a dose given at 9:00 AM local time.

Where this trips people up

Test suites often only generate current-timestamp values, which hides bugs in how a system handles historical doses (date-only, no time component) or doses logged after the fact with a backdated RXA-3. Some parsers silently default a missing time portion to midnight, which can shift a dose into the wrong reporting period for registry submissions — a bug that never shows up until someone reconciles monthly counts against the source system.

→

HL7 v2 RXA Segment Guide: Fields, Format, and Testing Gotchas

→

HL7 ADT Messages: A01 through A08 Explained

→

Regression Testing for EHR Upgrades: A Complete Guide

Stop hand-crafting timestamp edge cases

Synthibase generates synthetic RXA segments across the full range of date/time precisions — same-day, backdated, and timezone-shifted — so your parser gets exercised against the cases real feeds actually send.

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