diff --git a/docs/release.md b/docs/release.md
index 923cc98..451343b 100644
--- a/docs/release.md
+++ b/docs/release.md
@@ -6,7 +6,9 @@
 machine expects to find applications: `/Applications` on macOS, or the package manager on Linux.
 It is the same command whether or not the app is already installed, so it doubles as the update.
 On macOS it asks a running copy to quit first, because replacing a bundle under a live process
-leaves it half old and half new. `just uninstall` reverses it and leaves the data directory alone.
+leaves it half old and half new, and starts the new one once it is in place, so the copy on screen
+is never older than the copy installed. `just uninstall` reverses it and leaves the data directory
+alone.
 
 The local build skips the dmg and builds only the `.app`, since nothing about copying a bundle
 into place needs a disk image and building one is the slowest part of a mac bundle. That makes a
diff --git a/justfile b/justfile
index 526e0c0..ccb5c8e 100644
--- a/justfile
+++ b/justfile
@@ -37,7 +37,7 @@ build:
       *)      echo "just: no local build for $(uname -s); macOS and Linux are the desktop targets." >&2; exit 1 ;;
     esac
 
-# Build and install, replacing whatever version is already installed.
+# Build, install over whatever version is already installed, and start the new one.
 install: build
     #!/usr/bin/env bash
     set -euo pipefail
@@ -75,6 +75,7 @@ _install-macos:
     cp -R "$src" "$dest"
     version=$(defaults read "$dest/Contents/Info.plist" CFBundleShortVersionString 2> /dev/null || echo "?")
     echo "Installed $version to $dest"
+    open "$dest"
 
 _install-linux:
     #!/usr/bin/env bash
diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 1f358c5..44668e8 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -2276,7 +2276,7 @@ checksum = "112b39cec0b298b6c1999fee3e31427f74f676e4cb9879ed1a121b43661a4154"
 
 [[package]]
 name = "margin-calendar"
-version = "0.0.4"
+version = "0.0.5"
 dependencies = [
  "base64 0.22.1",
  "block2",
diff --git a/src/useClock.ts b/src/useClock.ts
index b9cd80c..92742d8 100644
--- a/src/useClock.ts
+++ b/src/useClock.ts
@@ -1,15 +1,15 @@
 // The wall clock, at the two granularities anything on the grid cares about: the minute the now
 // line moves on, and the hour the fit holds open around it.
 //
-// Both schedule off the clock rather than off an interval, so a tab that was asleep and a machine
-// that woke up catch up on the next tick instead of drifting further out every hour. A timer is
-// still a timer, though: one set before the lid closed can fire long after its wall-clock
-// deadline, and a hidden window's timers run late or not at all. So the window coming back, as a
-// focus or a visibility change, is read as a tick of its own.
+// Both are read off the clock once a minute rather than counted down to. A timer's deadline is
+// measured in time the machine spent awake, so one set for the top of the hour before the lid
+// closed is still waiting out the rest of that hour when it opens, however late it is by then.
+// Reading once a minute puts a minute on how far behind either can be; the window coming back, as
+// a focus or a visibility change, is read as a tick of its own so it is usually less.
 //
 // They are separate hooks because they are separate rerenders. The minute belongs to the one
-// component that draws the line; putting the fit on that tick would solve the whole axis sixty
-// times an hour to answer a question that changes once.
+// component that draws the line. The hour is read as often but only changes once an hour, and a
+// state set to the value it already holds rerenders nothing.
 
 import { useEffect, useState } from "react";
 
@@ -22,20 +22,12 @@ function hourStart(ms: number): number {
   return d.getTime();
 }
 
-/** The next one. `setMinutes(60)` rolls the date over for us, daylight saving and all. */
-function nextHourStart(ms: number): number {
-  const d = new Date(ms);
-  d.setMinutes(60, 0, 0);
-  return d.getTime();
-}
-
-function useTick<T>(read: (now: number) => T, next: (now: number) => number): T {
+function useTick<T>(read: (now: number) => T): T {
   const [value, setValue] = useState(() => read(Date.now()));
   useEffect(() => {
     let timer = 0;
     const schedule = () => {
-      const now = Date.now();
-      timer = window.setTimeout(tick, Math.max(0, next(now) - now));
+      timer = window.setTimeout(tick, MINUTE - (Date.now() % MINUTE));
     };
     const tick = () => {
       window.clearTimeout(timer);
@@ -53,25 +45,24 @@ function useTick<T>(read: (now: number) => T, next: (now: number) => number): T
       document.removeEventListener("visibilitychange", woke);
       window.removeEventListener("focus", woke);
     };
-    // Both callbacks are module-level functions in every caller, so there is nothing to rebind.
-  }, [read, next]);
+    // `read` is a module-level function in every caller, so there is nothing to rebind.
+  }, [read]);
   return value;
 }
 
 const now = (ms: number) => ms;
-const nextMinute = (ms: number) => ms + MINUTE - (ms % MINUTE);
 
 /** Now, refreshed on every wall-clock minute. */
 export function useMinuteTick(): number {
-  return useTick(now, nextMinute);
+  return useTick(now);
 }
 
 /**
- * The top of the hour it is now, refreshed when the clock turns over into the next one.
+ * The top of the hour it is now, read every minute and changed once an hour.
  *
  * Returning the hour rather than the instant is what makes this cheap to depend on: the value is
  * identical for a whole hour, so a memo keyed on it recomputes once, when the answer changed.
  */
 export function useHourStart(): number {
-  return useTick(hourStart, nextHourStart);
+  return useTick(hourStart);
 }
diff --git a/tests/grid.spec.ts b/tests/grid.spec.ts
index 01ba166..bf2d1d8 100644
--- a/tests/grid.spec.ts
+++ b/tests/grid.spec.ts
@@ -280,6 +280,52 @@ test.describe("the hour it is now", () => {
     expect((await axis(page)).map((entry) => entry.text)).not.toContain("11pm");
     await expect(page.locator(".grid-now")).toHaveCount(0);
   });
+
+  // The two below are about an app left open, so the clock is a running one rather than a pinned
+  // instant: `install` lets it be moved, and the strip that reads "8pm to 10pm" only exists once
+  // the hour it holds open has moved from nine to ten.
+  test("moves on with the clock while the app stays open", async ({ page }) => {
+    await page.clock.install({ time: clockAt(21, 58) });
+    await openApp(page);
+    await page.clock.pauseAt(clockAt(21, 59));
+    const before = (await axis(page)).map((entry) => entry.text);
+    expect(before).toContain("9pm");
+    expect(before).not.toContain("10pm");
+
+    await page.clock.runFor(2 * 60_000);
+
+    await expect(page.locator(".grid-strip", { hasText: "8pm to 10pm" })).toHaveCount(1);
+    const after = (await axis(page)).map((entry) => entry.text);
+    expect(after).toContain("10pm");
+    expect(after).not.toContain("9pm");
+    await expect(page.locator(".grid-now")).toHaveCount(1);
+  });
+
+  test("catches up when the clock jumped, as it does after the lid was closed", async ({ page }) => {
+    await page.clock.install({ time: clockAt(21, 30) });
+    await openApp(page);
+    await page.clock.pauseAt(clockAt(21, 31));
+    expect((await axis(page)).map((entry) => entry.text)).toContain("9pm");
+
+    // Asleep, the wall clock moves on and the timers do not: one set for the top of the hour is
+    // still waiting for the rest of its half hour when the machine wakes at five past ten. What
+    // the app gets is one minute of being awake.
+    await page.clock.setSystemTime(clockAt(22, 5));
+    await page.clock.runFor(60_000);
+
+    await expect(page.locator(".grid-strip", { hasText: "8pm to 10pm" })).toHaveCount(1);
+    const hours = (await axis(page)).map((entry) => entry.text);
+    expect(hours).toContain("10pm");
+    expect(hours).not.toContain("9pm");
+    await expect(page.locator(".grid-now")).toHaveCount(1);
+
+    const line = await box(page.locator(".grid-now"));
+    const row = (await gridFit(page)).rowHeight;
+    const ten = (await axis(page)).find((entry) => entry.text === "10pm");
+    const canvas = await box(page.locator(".grid-canvas"));
+    expect(line.top - canvas.top).toBeGreaterThan(ten!.y);
+    expect(line.top - canvas.top).toBeLessThan(ten!.y + row);
+  });
 });
 
 test.describe("the all-day band", () => {