If SCH-1 and SCH-2 are the appointment's name tags, SCH-11 is where the actual clock lives. It is also the densest field in the segment, and the one most likely to be built wrong in hand-written test fixtures.
Quick answer
SCH-11 (Appointment Timing Quantity) is a repeatable, multi-component field that encodes when the appointment actually happens — most importantly the precise start and end date-times of the scheduled slot, alongside optional repeat-pattern and priority components.
What this field contains
Component 4
Start Date/Time — the date and time the appointment begins, expressed as a full HL7 timestamp down to the second
Component 5
End Date/Time — the date and time the appointment is expected to end; together with the start, this defines the actual slot on the calendar
Earlier components
Quantity, interval, repeat pattern — leading components can describe a recurring schedule, but for a single-occurrence appointment these are typically left blank
Repetition
Field repeats with ~ — the whole field can repeat to describe multiple time windows for the same appointment, separated by a tilde
Example
Synthetic example Generated by Synthibase
SCH|APT88213^SYNTHIB|FIL55021^SYNTHIB|||||FOLLOWUP^Follow-up Visit^SYNTHIBLOCAL|OFFICE^Office Visit^SYNTHIBLOCAL|30|MIN|^^^20260728090000^20260728093000||||||||||||||SCHEDULED^Scheduled^SYNTHIBLOCAL
SCH-11 here is ^^^20260728090000^20260728093000 — a fake 09:00 to 09:30 slot with the leading repeat-pattern components left empty.
Where this trips people up
It's easy to miscount the leading empty components and place the start date-time one slot too early or too late, which silently shifts every appointment in a test batch by one component position. The message still parses without error, so the mistake only surfaces when someone notices every synthetic appointment start time looks suspiciously identical to its end time — or vice versa.
Never miscount a component position again
Synthibase builds SCH-11 timing quantities programmatically from real calendar logic, guaranteeing correctly positioned start and end date-times across every synthetic scheduling message you generate.
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