diff --git a/pyproject.toml b/pyproject.toml
index b7db2cc1d7b..6145db57902 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -277,6 +277,7 @@ proxy-dev = [
 ]
 ci = [
     "psutil==7.2.2",
+    "tzdata==2026.2",
     # These are lazily imported at call sites; keep them out of core deps to
     # avoid bloating the base SDK install (google-generativeai pulls grpcio +
     # protobuf, Pillow is a compiled C extension).
diff --git a/uv.lock b/uv.lock
index 62187d596ec..2dec937800c 100644
--- a/uv.lock
+++ b/uv.lock
@@ -5230,6 +5230,7 @@ ci = [
     { name = "pytest-retry" },
     { name = "tenacity" },
     { name = "traceloop-sdk" },
+    { name = "tzdata" },
 ]
 dev = [
     { name = "basedpyright" },
@@ -5468,6 +5469,7 @@ ci = [
     { name = "pytest-retry", specifier = "==1.7.0" },
     { name = "tenacity", specifier = "==8.5.0" },
     { name = "traceloop-sdk", specifier = "==0.34.0" },
+    { name = "tzdata", specifier = "==2026.2" },
 ]
 dev = [
     { name = "basedpyright", specifier = "==1.39.7" },