diff --git a/requirements.in b/requirements.in
index 478697bb..5eaf277f 100644
--- a/requirements.in
+++ b/requirements.in
@@ -2,7 +2,7 @@ pelican[markdown]==4.12.0
 pytz==2026.5
 ghp-import==2.1.0
 pathspec==1.1.1
-python-dateutil==2.9.0.post0
+python-dateutil==3.0.0
 PyYAML==6.0.3
 six==1.17.0
 yamllint==1.38.0
diff --git a/requirements.txt b/requirements.txt
index b303d732..4943e92a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -327,9 +327,9 @@ pygments==2.19.2 \
     # via
     #   pelican
     #   rich
-python-dateutil==2.9.0.post0 \
-    --hash=sha256:37dd54208da7e1cd875388217d5e00ebd4179249f90fb72437e91a35459a0ad3 \
-    --hash=sha256:a8b2bc7bffae282281c8140a97d3aa9c14da0b136dfe83f850eea9a5f7470427
+python-dateutil==3.0.0 \
+    --hash=sha256:3c79630202e4152c6add678446984236efe4f57e84d8e892aab0637bab82e9fd \
+    --hash=sha256:7ebcb3c29a92f3ceafe79a7a48a5c45677e9e004bbeec5742ac0bbb00560b7a2
     # via
     #   -r requirements.in
     #   ghp-import
@@ -433,6 +433,12 @@ typing-extensions==4.15.0 \
     --hash=sha256:0cea48d173cc12fa28ecabc3b837ea3cf6f38c6d1136f85cbaaf598984861466 \
     --hash=sha256:f0fa19c6845758ab08074a0cfa8b7aecb71c999ca73d62883bc25cc018c4e548
     # via beautifulsoup4
+tzdata==2026.5 \
+    --hash=sha256:8cc73c0a0bfca7dbfa59235d60b2eff82231dee33f53d206db1acd9173cfc0a7 \
+    --hash=sha256:8cc73c0a0bfca7dbfa59235d60b2eff82231dee33f53d206db1acd9173cfc0a7 \
+    --hash=sha256:b683bd1b6659ddcd810ff02ad09ba821d4bf1065072805063eb35c49617905ac \
+    --hash=sha256:b683bd1b6659ddcd810ff02ad09ba821d4bf1065072805063eb35c49617905ac
+    # via python-dateutil
 unidecode==1.4.0 \
     --hash=sha256:c3c7606c27503ad8d501270406e345ddb480a7b5f38827eafe4fa82a137f0021 \
     --hash=sha256:ce35985008338b676573023acc382d62c264f307c8f7963733405add37ea2b23