diff --git a/spec/SDD-Keylime-Monitoring-Tool.md b/spec/SDD-Keylime-Monitoring-Tool.md
index 2c8079e..8c29a03 100644
--- a/spec/SDD-Keylime-Monitoring-Tool.md
+++ b/spec/SDD-Keylime-Monitoring-Tool.md
@@ -1036,6 +1036,7 @@ Maximum 5 parallel concurrent log fetches to the Verifier API, enforced via Toki
 | Vite proxy for backend health checks | Avoids CORS failures in dev mode when probing backend settings endpoint | FR-077 |
 | Mock/Production URL presets | Reduces configuration friction; auto-detects active mode from saved URLs | FR-074 |
 | `#[serde(default)]` on Keylime models | Tolerates missing/renamed fields across Keylime API versions without breaking deserialization | NFR-002 |
+| Timezone auto-detect with manual override | Default to browser timezone for zero-config; IANA dropdown for operators in different timezones than their fleet | FR-078 |
 
 ---
 
@@ -1131,6 +1132,7 @@ Maximum 5 parallel concurrent log fetches to the Verifier API, enforced via Toki
 | FR-075 | 3.8.1 | `SettingsStore`, TOML persistence with atomic writes |
 | FR-076 | 3.2.2 | Layout hamburger button, sidebar CSS transition |
 | FR-077 | 3.2.2, 3.7.3 | 1s polling via `refetchInterval`, `probe_verifier()`/`probe_registrar()` |
+| FR-078 | 3.8.2 | `visualizationStore`: timezone with auto-detect, IANA timezone dropdown in Settings |
 
 ### 6.2 Non-Functional Requirements
 
diff --git a/spec/SRS-Keylime-Monitoring-Tool.md b/spec/SRS-Keylime-Monitoring-Tool.md
index 41556de..c83814f 100644
--- a/spec/SRS-Keylime-Monitoring-Tool.md
+++ b/spec/SRS-Keylime-Monitoring-Tool.md
@@ -111,6 +111,7 @@ The System transforms Keylime from a CLI-driven security tool into a visual oper
 | FR-075 | TOML config file persistence for backend settings | MUST | Settings - Configuration Persistence |
 | FR-076 | Sidebar visibility toggle (hamburger button) | MUST | Dashboard - Navigation Structure |
 | FR-077 | Webtool backend health check with polling | MUST | Integration Status - Backend Connectivity |
+| FR-078 | Timezone selection with auto-detect | SHOULD | Settings - Visualization |
 
 ### 2.2 Non-Functional Requirements
 
@@ -2405,6 +2406,36 @@ Feature: Webtool Backend Health Check
     And the disabled sections MUST be re-enabled automatically
 ```
 
+### FR-078: Timezone Selection with Auto-Detect
+
+**Description:** The System SHOULD provide a timezone setting in the Visualization Settings section. The user MUST be able to either auto-detect the browser timezone or manually select a timezone from a dropdown list of IANA timezone identifiers (e.g. `Europe/Madrid`, `America/New_York`, `UTC`). When auto-detect is active, the dropdown MUST be disabled. The selected timezone MUST be persisted in localStorage via the visualization store and applied to all timestamp rendering across the dashboard.
+
+**Trace:** Settings - Visualization
+
+```gherkin
+Feature: Timezone Selection
+
+  Scenario: Auto-detect browser timezone
+    Given the user navigates to Settings > Visualization
+    When the user clicks the "Auto-Detect" button
+    Then the timezone MUST be set to the browser's local timezone
+    And the timezone dropdown MUST be disabled
+    And the preference MUST persist across sessions via localStorage
+
+  Scenario: Manual timezone selection
+    Given the user navigates to Settings > Visualization
+    And auto-detect is not active
+    When the user selects "UTC" from the timezone dropdown
+    Then all timestamps across the dashboard MUST render in UTC
+    And the preference MUST persist across sessions via localStorage
+
+  Scenario: Switching from auto-detect to manual
+    Given auto-detect is active and the timezone dropdown is disabled
+    When the user clicks the "Auto-Detect" button again to deactivate it
+    Then the timezone dropdown MUST become enabled
+    And the user MUST be able to select a different timezone
+```
+
 ---
 
 ## 4. Non-Functional Requirements Detail