diff --git a/python/changelog.d/857.fix.md b/python/changelog.d/857.fix.md
new file mode 100644
index 000000000..357c35208
--- /dev/null
+++ b/python/changelog.d/857.fix.md
@@ -0,0 +1 @@
+Run, annotation, test step, and data import time bounds are nanosecond timestamps, matching channel data, so a time axis built from them lines up with `get_data`.
diff --git a/python/lib/sift_client/_tests/resources/test_data_imports.py b/python/lib/sift_client/_tests/resources/test_data_imports.py
index f3bb9c2ea..a14f712c1 100644
--- a/python/lib/sift_client/_tests/resources/test_data_imports.py
+++ b/python/lib/sift_client/_tests/resources/test_data_imports.py
@@ -9,6 +9,7 @@
 
 import pandas as pd
 import pytest
+from google.protobuf.timestamp_pb2 import Timestamp
 from sift.common.type.v1.channel_config_pb2 import ChannelConfig as ChannelConfigProto
 from sift.data_imports.v2.data_imports_pb2 import (
     DATA_IMPORT_STATUS_FAILED,
@@ -38,6 +39,7 @@
     resolve_data_type_key,
 )
 from sift_client._internal.util.time_column import infer_time_column
+from sift_client._tests.sift_types.channel_time import assert_axis_matches_channel
 from sift_client.resources import DataImportAPI, DataImportAPIAsync
 from sift_client.sift_types.channel import ChannelDataType
 from sift_client.sift_types.data_import import (
@@ -1280,6 +1282,20 @@ def test_unset_optionals_are_none(self):
         assert data_import.data_start_time is None
         assert data_import.data_stop_time is None
 
+    def test_bounds_match_channel_timestamp_resolution(self):
+        """Import bounds use the same integer scale as channel data."""
+        start = Timestamp(seconds=1735689600, nanos=123456789)
+        stop = Timestamp(seconds=1735689601, nanos=0)
+        proto = _data_import_proto()
+        proto.data_start_time.CopyFrom(start)
+        proto.data_stop_time.CopyFrom(stop)
+
+        data_import = DataImport._from_proto(proto)
+
+        assert_axis_matches_channel(
+            data_import.data_start_time, data_import.data_stop_time, start, stop
+        )
+
 
 class TestDataImportsGet:
     @pytest.mark.asyncio
diff --git a/python/lib/sift_client/_tests/sift_types/channel_time.py b/python/lib/sift_client/_tests/sift_types/channel_time.py
new file mode 100644
index 000000000..aab29d07b
--- /dev/null
+++ b/python/lib/sift_client/_tests/sift_types/channel_time.py
@@ -0,0 +1,51 @@
+"""Shared check that a time axis matches the index ``get_data`` builds."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import numpy as np
+import pandas as pd
+from google.protobuf.any_pb2 import Any
+from sift.common.type.v1.channel_data_type_pb2 import CHANNEL_DATA_TYPE_DOUBLE
+from sift.data.v2.data_pb2 import DoubleValue, DoubleValues, Metadata
+
+from sift_client._internal.low_level_wrappers.data import DataLowLevelClient
+
+if TYPE_CHECKING:
+    from google.protobuf.timestamp_pb2 import Timestamp
+
+
+def channel_index(*timestamps: Timestamp) -> pd.DatetimeIndex:
+    """Index ``get_data`` builds for double-channel samples at these times."""
+    values = DoubleValues(
+        metadata=Metadata(
+            data_type=CHANNEL_DATA_TYPE_DOUBLE,
+            sampled_ms=0,
+            channel=Metadata.Channel(name="voltage"),
+        ),
+        values=[DoubleValue(timestamp=ts, value=1.0) for ts in timestamps],
+    )
+    packed = Any()
+    packed.Pack(values)
+    # ``Pack`` writes ``type.googleapis.com/...``. The data parser reads the
+    # ``sift.data`` prefix the API sends.
+    packed.type_url = "sift.data.v2.DoubleValues"
+    frame = DataLowLevelClient.try_deserialize_channel_data(packed)["voltage"]
+    index = frame.index
+    assert isinstance(index, pd.DatetimeIndex)
+    return index
+
+
+def _integer_view(index: pd.DatetimeIndex) -> list[int]:
+    """Integers in the index's own unit, the scale interpolation uses."""
+    return [int(value) for value in np.asarray(index, dtype=np.int64)]
+
+
+def assert_axis_matches_channel(start, stop, *timestamps: Timestamp) -> None:
+    """A ``date_range`` across these bounds uses the channel index scale."""
+    samples = channel_index(*timestamps)
+    axis = pd.date_range(start, stop, periods=2)
+    assert str(samples.dtype).startswith("datetime64[ns")
+    assert axis.dtype == samples.dtype
+    assert _integer_view(axis) == _integer_view(samples)
diff --git a/python/lib/sift_client/_tests/sift_types/test_annotation.py b/python/lib/sift_client/_tests/sift_types/test_annotation.py
index 6ac3a751c..6778e4c84 100644
--- a/python/lib/sift_client/_tests/sift_types/test_annotation.py
+++ b/python/lib/sift_client/_tests/sift_types/test_annotation.py
@@ -4,9 +4,12 @@
 from unittest.mock import MagicMock
 
 import pytest
+from google.protobuf.timestamp_pb2 import Timestamp
+from sift.annotations.v1.annotations_pb2 import Annotation as AnnotationProto
 from sift.channels.v3.channels_pb2 import Channel as ChannelProto
 from sift.common.type.v1.channel_data_type_pb2 import ChannelDataType as ChannelDataTypeProto
 
+from sift_client._tests.sift_types.channel_time import assert_axis_matches_channel
 from sift_client.sift_types import Annotation
 from sift_client.sift_types.annotation import (
     AnnotationCommentElement,
@@ -249,3 +252,19 @@ def test_state_verbs_forward_to_the_resource(self, mock_annotation, mock_client)
                 getattr(mock_client.annotations, verb).assert_called_once_with(
                     annotation=mock_annotation
                 )
+
+
+class TestAnnotationFromProto:
+    def test_bounds_match_channel_timestamp_resolution(self):
+        """Annotation bounds use the same integer scale as channel data."""
+        start = Timestamp(seconds=1735689600, nanos=123456789)
+        stop = Timestamp(seconds=1735689601, nanos=0)
+        proto = AnnotationProto(annotation_id="a", name="n", description="")
+        proto.created_date.FromDatetime(datetime(2025, 1, 1, tzinfo=timezone.utc))
+        proto.modified_date.CopyFrom(proto.created_date)
+        proto.start_time.CopyFrom(start)
+        proto.end_time.CopyFrom(stop)
+
+        annotation = Annotation._from_proto(proto)
+
+        assert_axis_matches_channel(annotation.start_time, annotation.end_time, start, stop)
diff --git a/python/lib/sift_client/_tests/sift_types/test_results.py b/python/lib/sift_client/_tests/sift_types/test_results.py
index c1530f1e7..1b50668bc 100644
--- a/python/lib/sift_client/_tests/sift_types/test_results.py
+++ b/python/lib/sift_client/_tests/sift_types/test_results.py
@@ -8,6 +8,7 @@
 from unittest.mock import MagicMock, call
 
 import pytest
+from google.protobuf.timestamp_pb2 import Timestamp
 from sift.test_reports.v1.test_reports_pb2 import (
     TestMeasurement as TestMeasurementProto,
 )
@@ -15,6 +16,7 @@
     TestStep as TestStepProto,
 )
 
+from sift_client._tests.sift_types.channel_time import assert_axis_matches_channel
 from sift_client.sift_types.channel import Channel, ChannelDataType
 from sift_client.sift_types.test_report import (
     ErrorInfo,
@@ -496,3 +498,22 @@ def test_step_from_proto_handles_absent_metadata(self):
         proto.end_time.FromDatetime(datetime.now(timezone.utc))
         step = TestStep._from_proto(proto)
         assert step.metadata is None
+
+    def test_bounds_match_channel_timestamp_resolution(self):
+        """Step bounds use the same integer scale as channel data."""
+        start = Timestamp(seconds=1735689600, nanos=123456789)
+        stop = Timestamp(seconds=1735689601, nanos=0)
+        proto = TestStepProto(
+            test_step_id="step_abc",
+            test_report_id="report_789",
+            name="Step",
+            step_type=TestStepType.ACTION.value,
+            step_path="1",
+            status=TestStatus.IN_PROGRESS.value,
+        )
+        proto.start_time.CopyFrom(start)
+        proto.end_time.CopyFrom(stop)
+
+        step = TestStep._from_proto(proto)
+
+        assert_axis_matches_channel(step.start_time, step.end_time, start, stop)
diff --git a/python/lib/sift_client/_tests/sift_types/test_run.py b/python/lib/sift_client/_tests/sift_types/test_run.py
index 58695efdf..b94b59f56 100644
--- a/python/lib/sift_client/_tests/sift_types/test_run.py
+++ b/python/lib/sift_client/_tests/sift_types/test_run.py
@@ -4,7 +4,10 @@
 from unittest.mock import MagicMock
 
 import pytest
+from google.protobuf.timestamp_pb2 import Timestamp
+from sift.runs.v2.runs_pb2 import Run as RunProto
 
+from sift_client._tests.sift_types.channel_time import assert_axis_matches_channel
 from sift_client.sift_types import Run
 from sift_client.sift_types.run import RunCreate, RunUpdate
 
@@ -134,6 +137,45 @@ def mock_run(mock_client):
 class TestRun:
     """Unit tests for Run model - tests properties and methods."""
 
+    def test_bounds_match_channel_timestamp_resolution(self):
+        """A time axis from run bounds matches the channel index for the same timestamps.
+
+        ``stop_time`` is an exact second. That instant prints the same as a
+        microsecond ``datetime`` and still disagrees when both are read as
+        integers.
+        """
+        start = Timestamp(seconds=1735689600, nanos=123456789)
+        stop = Timestamp(seconds=1735689601, nanos=0)
+        proto = RunProto(
+            run_id="r",
+            name="n",
+            description="",
+            created_by_user_id="u",
+            modified_by_user_id="u",
+            organization_id="o",
+        )
+        proto.created_date.FromDatetime(datetime(2025, 1, 1, tzinfo=timezone.utc))
+        proto.modified_date.CopyFrom(proto.created_date)
+        proto.start_time.CopyFrom(start)
+        proto.stop_time.CopyFrom(stop)
+
+        run = Run._from_proto(proto)
+        assert_axis_matches_channel(run.start_time, run.stop_time, start, stop)
+
+        unset = RunProto(
+            run_id="r",
+            name="n",
+            description="",
+            created_by_user_id="u",
+            modified_by_user_id="u",
+            organization_id="o",
+        )
+        unset.created_date.CopyFrom(proto.created_date)
+        unset.modified_date.CopyFrom(proto.modified_date)
+        unbounded = Run._from_proto(unset)
+        assert unbounded.start_time is None
+        assert unbounded.stop_time is None
+
     def test_assets_property_calls_client(self, mock_run, mock_client):
         """Test that assets property calls client.assets.list_ with correct parameters."""
         mock_client.assets.list_.return_value = []
diff --git a/python/lib/sift_client/sift_types/annotation.py b/python/lib/sift_client/sift_types/annotation.py
index 86f3d23c4..2cbb3e357 100644
--- a/python/lib/sift_client/sift_types/annotation.py
+++ b/python/lib/sift_client/sift_types/annotation.py
@@ -4,6 +4,7 @@
 from enum import Enum
 from typing import TYPE_CHECKING, ClassVar, Literal, cast
 
+import pandas as pd  # noqa: TC002
 from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
 from sift.annotation_logs.v1.annotation_logs_pb2 import (
     AnnotationCommentBodyElement as AnnotationCommentBodyElementProto,
@@ -43,6 +44,7 @@
     CreateAnnotationRequest as CreateAnnotationRequestProto,
 )
 
+from sift_client._internal.time import to_timestamp_nanos
 from sift_client.sift_types._base import (
     BaseType,
     MappingHelper,
@@ -105,13 +107,20 @@ def _linked_channel_to_proto(channel: Channel | CalculatedChannel) -> Annotation
 
 
 class Annotation(BaseType[AnnotationProto, "Annotation"]):
-    """Annotation model representing a time range on one or more assets."""
+    """Annotation model representing a time range on one or more assets.
+
+    ``start_time`` and ``end_time`` are nanosecond timestamps, the same
+    resolution as channel data from ``get_data``.
+    """
+
+    # pandas.Timestamp has no pydantic schema, so it is validated with isinstance.
+    model_config = ConfigDict(arbitrary_types_allowed=True)
 
     # Required fields
     name: str
     description: str
-    start_time: datetime
-    end_time: datetime
+    start_time: pd.Timestamp | datetime
+    end_time: pd.Timestamp | datetime
     annotation_type: AnnotationType
     organization_id: str
     created_date: datetime
@@ -141,8 +150,8 @@ def _from_proto(
             id_=proto.annotation_id,
             name=proto.name,
             description=proto.description,
-            start_time=proto.start_time.ToDatetime(tzinfo=timezone.utc),
-            end_time=proto.end_time.ToDatetime(tzinfo=timezone.utc),
+            start_time=to_timestamp_nanos(proto.start_time),
+            end_time=to_timestamp_nanos(proto.end_time),
             annotation_type=AnnotationType(proto.annotation_type),
             organization_id=proto.organization_id,
             created_date=proto.created_date.ToDatetime(tzinfo=timezone.utc),
diff --git a/python/lib/sift_client/sift_types/data_import.py b/python/lib/sift_client/sift_types/data_import.py
index 86688177b..0cb4c8322 100644
--- a/python/lib/sift_client/sift_types/data_import.py
+++ b/python/lib/sift_client/sift_types/data_import.py
@@ -1436,8 +1436,14 @@ class DataImport(BaseType[DataImportProto, "DataImport"]):
 
     The format-specific import config is not modeled here; read it off
     ``data_import.proto`` (e.g. ``data_import.proto.csv_config``).
+
+    ``data_start_time`` and ``data_stop_time`` are nanosecond timestamps,
+    the same resolution as channel data from ``get_data``.
     """
 
+    # pandas.Timestamp has no pydantic schema, so it is validated with isinstance.
+    model_config = ConfigDict(arbitrary_types_allowed=True)
+
     source_url: str | None
     status: DataImportStatus
     error_message: str | None
@@ -1450,8 +1456,8 @@ class DataImport(BaseType[DataImportProto, "DataImport"]):
     report_id: str | None
     asset_id: str | None
     # Time range of the imported data, not of the import itself.
-    data_start_time: datetime | None
-    data_stop_time: datetime | None
+    data_start_time: pd.Timestamp | datetime | None
+    data_stop_time: pd.Timestamp | datetime | None
 
     @classmethod
     def _from_proto(
@@ -1471,12 +1477,12 @@ def _from_proto(
             report_id=proto.report_id or None,
             asset_id=proto.asset_id or None,
             data_start_time=(
-                proto.data_start_time.ToDatetime(tzinfo=timezone.utc)
+                to_timestamp_nanos(proto.data_start_time)
                 if proto.HasField("data_start_time")
                 else None
             ),
             data_stop_time=(
-                proto.data_stop_time.ToDatetime(tzinfo=timezone.utc)
+                to_timestamp_nanos(proto.data_stop_time)
                 if proto.HasField("data_stop_time")
                 else None
             ),
diff --git a/python/lib/sift_client/sift_types/run.py b/python/lib/sift_client/sift_types/run.py
index b61968d7b..796db2ec4 100644
--- a/python/lib/sift_client/sift_types/run.py
+++ b/python/lib/sift_client/sift_types/run.py
@@ -3,10 +3,12 @@
 from datetime import datetime, timedelta, timezone
 from typing import TYPE_CHECKING, ClassVar
 
-from pydantic import model_validator
+import pandas as pd  # noqa: TC002
+from pydantic import ConfigDict, model_validator
 from sift.runs.v2.runs_pb2 import CreateRunRequest as CreateRunRequestProto
 from sift.runs.v2.runs_pb2 import Run as RunProto
 
+from sift_client._internal.time import to_timestamp_nanos
 from sift_client.sift_types._base import (
     BaseType,
     MappingHelper,
@@ -31,7 +33,16 @@
 
 
 class Run(BaseType[RunProto, "Run"], FileAttachmentsMixin):
-    """Run model representing a data collection run."""
+    """Run model representing a data collection run.
+
+    ``start_time`` and ``stop_time`` are nanosecond ``pandas.Timestamp``
+    values, the same resolution as channel data from ``get_data``. A time
+    axis built from these lines up with that data when both are read as
+    integers.
+    """
+
+    # pandas.Timestamp has no pydantic schema, so it is validated with isinstance.
+    model_config = ConfigDict(arbitrary_types_allowed=True)
 
     # Required fields
     name: str
@@ -50,8 +61,8 @@ class Run(BaseType[RunProto, "Run"], FileAttachmentsMixin):
     is_archived: bool
 
     # Optional fields
-    start_time: datetime | None
-    stop_time: datetime | None
+    start_time: pd.Timestamp | datetime | None
+    stop_time: pd.Timestamp | datetime | None
     duration: timedelta | None
     default_report_id: str | None
     client_key: str | None
@@ -68,14 +79,10 @@ def _from_proto(cls, proto: RunProto, sift_client: SiftClient | None = None) ->
             modified_by_user_id=proto.modified_by_user_id,
             organization_id=proto.organization_id,
             start_time=(
-                proto.start_time.ToDatetime(tzinfo=timezone.utc)
-                if proto.HasField("start_time")
-                else None
+                to_timestamp_nanos(proto.start_time) if proto.HasField("start_time") else None
             ),
             stop_time=(
-                proto.stop_time.ToDatetime(tzinfo=timezone.utc)
-                if proto.HasField("stop_time")
-                else None
+                to_timestamp_nanos(proto.stop_time) if proto.HasField("stop_time") else None
             ),
             duration=(proto.duration.ToTimedelta() if proto.HasField("duration") else None),
             name=proto.name,
diff --git a/python/lib/sift_client/sift_types/test_report.py b/python/lib/sift_client/sift_types/test_report.py
index b8b1f2236..9c21d3779 100644
--- a/python/lib/sift_client/sift_types/test_report.py
+++ b/python/lib/sift_client/sift_types/test_report.py
@@ -5,7 +5,8 @@
 from enum import Enum
 from typing import TYPE_CHECKING, ClassVar
 
-from pydantic import field_validator
+import pandas as pd  # noqa: TC002
+from pydantic import ConfigDict, field_validator
 from sift.test_reports.v1.test_reports_pb2 import (
     CreateTestReportRequest as CreateTestReportRequestProto,
 )
@@ -28,6 +29,7 @@
     TestStep as TestStepProto,
 )
 
+from sift_client._internal.time import to_timestamp_nanos
 from sift_client.sift_types._base import (
     BaseType,
     MappingHelper,
@@ -155,7 +157,14 @@ def to_proto(self) -> TestStepProto:
 
 
 class TestStep(BaseType[TestStepProto, "TestStep"], FileAttachmentsMixin, SimulatedMixin):
-    """TestStep model representing a step in a test."""
+    """TestStep model representing a step in a test.
+
+    ``start_time`` and ``end_time`` are nanosecond timestamps, the same
+    resolution as channel data from ``get_data``.
+    """
+
+    # pandas.Timestamp has no pydantic schema, so it is validated with isinstance.
+    model_config = ConfigDict(arbitrary_types_allowed=True)
 
     test_report_id: str
     parent_step_id: str | None = None
@@ -164,8 +173,8 @@ class TestStep(BaseType[TestStepProto, "TestStep"], FileAttachmentsMixin, Simula
     step_type: TestStepType
     step_path: str
     status: TestStatus
-    start_time: datetime
-    end_time: datetime
+    start_time: pd.Timestamp | datetime
+    end_time: pd.Timestamp | datetime
     error_info: ErrorInfo | None = None
     # NOTE: update() replaces this map wholesale. See TODO(metadata-mixin) in
     # sift_types/_mixins/metadata.py before adding keys at runtime.
@@ -187,8 +196,8 @@ def _from_proto(cls, proto: TestStepProto, sift_client: SiftClient | None = None
             step_type=TestStepType(proto.step_type),
             step_path=proto.step_path,
             status=TestStatus(proto.status),
-            start_time=proto.start_time.ToDatetime(tzinfo=timezone.utc),
-            end_time=proto.end_time.ToDatetime(tzinfo=timezone.utc),
+            start_time=to_timestamp_nanos(proto.start_time),
+            end_time=to_timestamp_nanos(proto.end_time),
             error_info=ErrorInfo._from_proto(proto.error_info, sift_client)
             if proto.HasField("error_info")
             else None,