diff --git a/services/web/migrations/20210726083523_convert_confirmedAt_strings_to_dates.js b/services/web/migrations/20210726083523_convert_confirmedAt_strings_to_dates.js
new file mode 100644
index 0000000000..1c9a599e50
--- /dev/null
+++ b/services/web/migrations/20210726083523_convert_confirmedAt_strings_to_dates.js
@@ -0,0 +1,9 @@
+const updateStringDates = require('../scripts/confirmed_at_to_dates.js')
+
+exports.migrate = async client => {
+  await updateStringDates()
+}
+
+exports.rollback = async client => {
+  /* nothing to do */
+}
diff --git a/services/web/scripts/confirmed_at_to_dates.js b/services/web/scripts/confirmed_at_to_dates.js
new file mode 100644
index 0000000000..1c63951047
--- /dev/null
+++ b/services/web/scripts/confirmed_at_to_dates.js
@@ -0,0 +1,54 @@
+const { db, waitForDb } = require('../app/src/infrastructure/mongodb')
+
+async function updateStringDates() {
+  await waitForDb()
+  const users = await db.users.aggregate([
+    { $unwind: { path: '$emails' } },
+    {
+      $match: { 'emails.confirmedAt': { $exists: true, $type: 'string' } },
+    },
+    {
+      $project: {
+        _id: 1,
+        'emails.email': 1,
+        'emails.confirmedAt': 1,
+      },
+    },
+  ])
+
+  let user
+  let count = 0
+  while ((user = await users.next())) {
+    count += 1
+    if (count % 10000 === 0) {
+      console.log(`processed ${count} users`)
+    }
+    const confirmedAt = user.emails.confirmedAt
+    const dateConfirmedAt = new Date(confirmedAt.replace(/ UTC$/, ''))
+    await db.users.updateOne(
+      {
+        _id: user._id,
+        'emails.email': user.emails.email,
+      },
+      {
+        $set: {
+          'emails.$.confirmedAt': dateConfirmedAt,
+        },
+      }
+    )
+  }
+  console.log(`Updated ${count} confirmedAt strings to dates!`)
+}
+
+if (!module.parent) {
+  updateStringDates()
+    .then(() => {
+      process.exit(0)
+    })
+    .catch(error => {
+      console.error(error)
+      process.exit(1)
+    })
+}
+
+module.exports = updateStringDates