diff --git a/frappe/core/doctype/security_settings/security_settings.py b/frappe/core/doctype/security_settings/security_settings.py
index be52808e01..478e4e909b 100644
--- a/frappe/core/doctype/security_settings/security_settings.py
+++ b/frappe/core/doctype/security_settings/security_settings.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2026, Frappe Technologies and contributors
 # For license information, please see license.txt
 
-from datetime import datetime
+from datetime import UTC, datetime
 
 import frappe
 import frappe.utils
@@ -33,13 +33,16 @@ class SecuritySettings(Document):
 
 	@property
 	def security_txt(self):
-		return "\n\n".join(
-			[
-				self.public_policy_section,
-				self.public_contacts_section,
-				self.public_languages_section,
-				self.public_expires_section,
-			]
+		return (
+			"\n\n".join(
+				[
+					self.public_policy_section,
+					self.public_contacts_section,
+					self.public_languages_section,
+					self.public_expires_section,
+				]
+			)
+			+ "\n"
 		)
 
 	@property
@@ -64,9 +67,11 @@ class SecuritySettings(Document):
 	@property
 	def public_expires_section(self):
 		expires = self.public_expires or frappe.utils.add_years(frappe.utils.now_datetime(), 1)
-		expires = (isinstance(expires, str) and datetime.fromisoformat(expires)) or expires
+		if isinstance(expires, str):
+			expires = datetime.fromisoformat(expires)
 		expires = expires.replace(microsecond=0)
-		value = expires.isoformat()
+		expires = expires.astimezone(UTC)
+		value = expires.strftime("%Y-%m-%dT%H:%M:%SZ")
 		return f"Expires: {value}"
 
 	def with_protocol(self, url: str, type_: str) -> str:
diff --git a/frappe/core/doctype/security_settings/test_security_settings.py b/frappe/core/doctype/security_settings/test_security_settings.py
index a398bb8b10..9052e407cc 100644
--- a/frappe/core/doctype/security_settings/test_security_settings.py
+++ b/frappe/core/doctype/security_settings/test_security_settings.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2026, Frappe Technologies and Contributors
 # License: MIT. See LICENSE
 
-from datetime import datetime, timedelta
+from datetime import UTC, datetime, timedelta
 
 import frappe
 from frappe.tests import UnitTestCase
@@ -240,7 +240,9 @@ class TestSecuritySettings(UnitTestCase):
 		doc.validate_expires()
 
 	def test_public_expires_section_future_date(self):
-		future_date = datetime(2027, 12, 31, 23, 59, 59)
+		from datetime import timezone
+
+		future_date = datetime(2027, 12, 31, 23, 59, 59, tzinfo=UTC)
 		doc = frappe.get_doc(
 			{
 				"doctype": "Security Settings",
@@ -248,17 +250,17 @@ class TestSecuritySettings(UnitTestCase):
 			}
 		)
 		section = doc.public_expires_section
-		self.assertIn("2027-12-31T23:59:59", section)
+		self.assertIn("2027-12-31T23:59:59Z", section)
 
 	def test_public_expires_section_string(self):
 		doc = frappe.get_doc(
 			{
 				"doctype": "Security Settings",
-				"public_expires": "2027-12-31T23:59:59",
+				"public_expires": "2027-12-31T23:59:59+00:00",
 			}
 		)
 		section = doc.public_expires_section
-		self.assertIn("2027-12-31T23:59:59", section)
+		self.assertIn("2027-12-31T23:59:59Z", section)
 
 	def test_public_expires_section_default(self):
 		doc = frappe.get_doc({"doctype": "Security Settings"})