From 85ee2c9fc0a2232ccee164619c85e35ac336b070 Mon Sep 17 00:00:00 2001
From: Miro <200482516+Mirochill@users.noreply.github.com>
Date: Sat, 23 May 2026 23:02:20 +0200
Subject: [PATCH] Fix Prometheus UTC timestamp formatting

Signed-off-by: Miro <200482516+Mirochill@users.noreply.github.com>
---
 CHANGELOG.md                    |  7 ++++-
 chaosreport/__init__.py         |  8 +++--
 tests/test_prometheus_charts.py | 54 +++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_prometheus_charts.py

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1edb712..c0d56da 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## [Unreleased][]
 
+### Fixed
+
+- Avoid the deprecated `datetime.utcfromtimestamp()` call when formatting
+  Prometheus chart labels.
+
 [Unreleased]: https://github.com/chaostoolkit/chaostoolkit-reporting/compare/0.18.0...HEAD
 
 ## [0.18.0][] - 2024-12-02
@@ -270,4 +275,4 @@
 
 ### Added
 
--   Initial release
\ No newline at end of file
+-   Initial release
diff --git a/chaosreport/__init__.py b/chaosreport/__init__.py
index 887b92e..c3b9c0a 100644
--- a/chaosreport/__init__.py
+++ b/chaosreport/__init__.py
@@ -10,7 +10,7 @@
 import subprocess
 import tempfile
 from base64 import b64encode
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from importlib.metadata import version, PackageNotFoundError
 from typing import Any, Dict, List
 
@@ -470,9 +470,11 @@ def generate_chart_from_prometheus(run: Run, export_format: str):
             # now we have our range of abscissa, let's map those
             # timestamps to formatted strings
             x = sorted(list(x))
-            fromts = datetime.utcfromtimestamp
             chart.x_labels = [
-                fromts(v).strftime("%Y-%m-%d\n %H:%M:%S") for v in x
+                datetime.fromtimestamp(v, timezone.utc).strftime(
+                    "%Y-%m-%d\n %H:%M:%S"
+                )
+                for v in x
             ]
             chart.x_labels_major = chart.x_labels[::10]
             chart.title = "Query -  {}".format(
diff --git a/tests/test_prometheus_charts.py b/tests/test_prometheus_charts.py
new file mode 100644
index 0000000..9edcd4b
--- /dev/null
+++ b/tests/test_prometheus_charts.py
@@ -0,0 +1,54 @@
+import chaosreport
+
+
+class LineChart:
+    instances = []
+
+    def __init__(self, **kwargs):
+        self.x_labels = []
+        self.x_labels_major = []
+        self.series = []
+        self.title = None
+        LineChart.instances.append(self)
+
+    def add(self, label, values, allow_interruptions=False):
+        self.series.append((label, values, allow_interruptions))
+
+    def render(self, **kwargs):
+        return b"<svg />"
+
+
+def test_generate_chart_from_prometheus_formats_labels_in_utc(monkeypatch):
+    LineChart.instances = []
+    monkeypatch.setattr(chaosreport.pygal, "Line", LineChart)
+
+    run = {
+        "activity": {
+            "provider": {
+                "arguments": {"query": "up"},
+            },
+        },
+        "output": {
+            "data": {
+                "resultType": "matrix",
+                "result": [
+                    {
+                        "metric": {"pod": "frontend"},
+                        "values": [
+                            (0, "1"),
+                            (3600, "2"),
+                        ],
+                    }
+                ],
+            },
+        },
+    }
+
+    chaosreport.generate_chart_from_prometheus(run, "html")
+
+    chart = LineChart.instances[0]
+    assert chart.x_labels == [
+        "1970-01-01\n 00:00:00",
+        "1970-01-01\n 01:00:00",
+    ]
+    assert chart.x_labels_major == ["1970-01-01\n 00:00:00"]