Improve timestamp handling and event navigation

server/monlet_server/services/ingestion.py

@@ -12,6 +12,7 @@ from ..models import Agent, Check, Event, Incident, NotificationOutbox
 from ..redaction import redact
 from ..schemas import CheckResultEvent, HeartbeatRequest
 from ..settings import get_settings
+from ..timeutil import to_utc
 
 INCIDENT_KEY_MAX = 256
 
@@ -37,11 +38,7 @@ def _incident_key(agent_id: str, ev: CheckResultEvent) -> str:
 
 
 async def upsert_agent_heartbeat(session: AsyncSession, hb: HeartbeatRequest) -> None:
-    observed = (
-        hb.observed_at.astimezone(UTC)
-        if hb.observed_at.tzinfo
-        else hb.observed_at.replace(tzinfo=UTC)
-    )
+    observed = to_utc(hb.observed_at)
     stmt = pg_insert(Agent).values(
         agent_id=hb.agent_id,
         hostname=hb.hostname,
@@ -71,7 +68,7 @@ async def _apply_incident(
     incident_key: str,
 ) -> tuple[bool, Incident | None]:
     """Return (transition, incident). transition True if open->resolved or none->open."""
-    observed = ev.observed_at
+    observed = to_utc(ev.observed_at)
     if ev.status == "ok":
         res = await session.execute(
             select(Incident).where(Incident.incident_key == incident_key, Incident.state == "open")
@@ -159,7 +156,7 @@ async def ingest_event(
     ev: CheckResultEvent,
 ) -> bool:
     """Return True if accepted, False if deduplicated."""
-    observed = ev.observed_at
+    observed = to_utc(ev.observed_at)
     output = redact(ev.output)
     incident_key = _incident_key(agent_id, ev)