diff --git a/poetry.lock b/poetry.lock
index 1e31c5f..9592505 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -4447,4 +4447,4 @@ testing = ["big-O", "jaraco.functools", "jaraco.itertools", "more-itertools", "p
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.8,<4.0"
-content-hash = "870e530cb9511cf2dd1660f028407321dbd8700b0a5ed0209d16867e8559b57b"
+content-hash = "6b78777677526c41d20fc7303321f99491f082b52fd545c4c848b7d6b8625468"
diff --git a/pyproject.toml b/pyproject.toml
index ca81d85..fe31528 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,6 +45,7 @@ pyarrow = "^15.0.0"
 bump-my-version = "^0.17.3"
 notebook = "^7.0.7"
 deptry = "^0.12.0"
+python-dateutil = "^2.8.2"
 
 [tool.poetry.group.docs.dependencies]
 mkdocs = "^1.4.2"
diff --git a/tests/test_traces_external.py b/tests/test_traces_external.py
new file mode 100644
index 0000000..3f018f1
--- /dev/null
+++ b/tests/test_traces_external.py
@@ -0,0 +1,27 @@
+import csv
+import os
+from datetime import datetime
+
+from dateutil.parser import parse as date_parse
+
+from traces import TimeSeries
+
+
+def test_csv():
+    filename = "sample.csv"
+    with open(filename, "w") as csvfile:
+        writer = csv.writer(csvfile)
+        writer.writerow(["hour", "value"])
+        writer.writerow(["2000-01-01 10:00am", "15"])
+        writer.writerow(["2000-01-01 11:00am", "34"])
+        writer.writerow(["2000-01-01 12:00pm", "19"])
+        writer.writerow(["2000-01-01 1:00pm", "nan"])
+        writer.writerow(["2000-01-01 2:00pm", "18"])
+        writer.writerow(["2000-01-01 3:00pm", "nan"])
+
+    ts = TimeSeries.from_csv(filename, time_transform=date_parse)
+    os.remove(filename)
+
+    assert ts[datetime(2000, 1, 1, 9)] is None
+    assert ts[datetime(2000, 1, 1, 10, 30)] == "15"
+    assert ts[datetime(2000, 1, 1, 20)] == "nan"
diff --git a/traces/timeseries.py b/traces/timeseries.py
index 6be9572..6c6c615 100644
--- a/traces/timeseries.py
+++ b/traces/timeseries.py
@@ -808,9 +808,7 @@ def merge(cls, ts_list, compact=True, operation=None):
 
     @staticmethod
     def csv_time_transform(raw):
-        from dateutil.parser import parse
-
-        return parse(raw)
+        return datetime.datetime.strptime(raw, "%Y-%m-%d %H:%M:%S")
 
     @staticmethod
     def csv_value_transform(raw):