diff --git a/data/patches/client-stats.js b/data/patches/client-stats.js
new file mode 100644
index 0000000..614eaa5
--- /dev/null
+++ b/data/patches/client-stats.js
@@ -0,0 +1,35 @@
+'use strict';
+
+/* globals db */
+
+const clients = db.clients.find();
+while (clients.hasNext()) {
+  let timeWorked = 0, billable = 0;
+
+  const client = clients.next();
+  const sessions = db.tasksessions.find({ client: client._id });
+  while (sessions.hasNext()) {
+    const session = sessions.next();
+    timeWorked += session.duration;
+    billable += session.hourlyRate * (session.duration / 3600);
+  }
+
+  /*
+   * Fix some JavaScript goofiness with numbers (round correctly to 2nd decimal
+   * digit).
+   */
+  billable = Math.round((billable + Number.EPSILON) * 100) / 100;
+
+  print(`client: ${client._id}:${client.name} time:${timeWorked} bill:${billable}`);
+  db.clients.updateOne(
+    { _id: client._id },
+    {
+      $set: {
+        weeklyTotals: {
+          timeWorked,
+          billable,
+        },
+      },
+    },
+  );
+}
\ No newline at end of file