diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1a3a219..65b7d78 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.1.16] — 2026-02-23
+
+### Changed
+- Updated Timer screen summary metrics: replaced `Magnitude` with `C1-C4 Duration` (computed from first to last contact times) and renamed `Central Duration` to `Totality Duration` for clearer eclipse-phase wording.
+- Bumped `apps/mobile` version to `1.1.16`.
+
 ## [1.1.15] — 2026-02-23
 
 ### Removed
diff --git a/apps/mobile/package.json b/apps/mobile/package.json
index 05816df..26ac883 100644
--- a/apps/mobile/package.json
+++ b/apps/mobile/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@eclipse-timer/mobile",
-  "version": "1.1.15",
+  "version": "1.1.16",
   "private": true,
   "main": "index.js",
   "scripts": {
diff --git a/apps/mobile/src/screens/TimerScreen.tsx b/apps/mobile/src/screens/TimerScreen.tsx
index f1c6f76..30e3d7e 100644
--- a/apps/mobile/src/screens/TimerScreen.tsx
+++ b/apps/mobile/src/screens/TimerScreen.tsx
@@ -38,11 +38,6 @@ function localKindLabel(kind: "none" | "partial" | "total" | "annular") {
   return "None";
 }
 
-function formatMagnitude(magnitude?: number) {
-  if (typeof magnitude !== "number" || !Number.isFinite(magnitude)) return "--";
-  return magnitude.toFixed(3);
-}
-
 function formatDuration(seconds?: number) {
   if (typeof seconds !== "number" || !Number.isFinite(seconds) || seconds <= 0) return "--";
   const totalSeconds = Math.round(seconds);
@@ -51,6 +46,20 @@ function formatDuration(seconds?: number) {
   return `${mm}m ${String(ss).padStart(2, "0")}s`;
 }
 
+function parseUtcTimestamp(iso?: string) {
+  if (!iso) return undefined;
+  const timestamp = Date.parse(iso);
+  if (!Number.isFinite(timestamp)) return undefined;
+  return timestamp;
+}
+
+function formatC1ToC4Duration(result: Circumstances) {
+  const c1 = parseUtcTimestamp(result.c1Utc);
+  const c4 = parseUtcTimestamp(result.c4Utc);
+  if (c1 === undefined || c4 === undefined || c4 <= c1) return "--";
+  return formatDuration((c4 - c1) / 1000);
+}
+
 function formatCardinalCoord(
   value: number,
   positiveHemisphere: string,
@@ -742,11 +751,11 @@ export default function TimerScreen({
                   </Text>
                 </View>
                 <View style={styles.metricTile}>
-                  <Text style={styles.metricLabel}>Magnitude</Text>
-                  <Text style={styles.metricValue}>{formatMagnitude(timer.result.magnitude)}</Text>
+                  <Text style={styles.metricLabel}>C1-C4 Duration</Text>
+                  <Text style={styles.metricValue}>{formatC1ToC4Duration(timer.result)}</Text>
                 </View>
                 <View style={styles.metricTile}>
-                  <Text style={styles.metricLabel}>Central Duration</Text>
+                  <Text style={styles.metricLabel}>Totality Duration</Text>
                   <Text style={styles.metricValue}>
                     {formatDuration(timer.result.durationSeconds)}
                   </Text>