diff --git a/README.md b/README.md
index 2315203..a323132 100644
--- a/README.md
+++ b/README.md
@@ -143,6 +143,12 @@ python -m server
 
 to spawn the server-side part, listening on `localhost:8081`.
 
+### Updating
+
+Database migrations are in the `scripts/migrations` folder, labelled by
+versions. You should run them in order from your current versions to the
+latest one when you upgrade.
+
 ### Useful scripts for dev
 
 You can run `scripts/gps_to_gpx.py` on your GPX trace to create a
diff --git a/scripts/migrations/0.3.py b/scripts/migrations/0.3.py
new file mode 100644
index 0000000..60a1c14
--- /dev/null
+++ b/scripts/migrations/0.3.py
@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+"""
+Database migration from < 0.3 to 0.3 version.
+"""
+import os
+import sys
+
+import peewee
+
+SCRIPT_DIRECTORY = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.abspath(os.path.join(SCRIPT_DIRECTORY, '..', '..')))
+
+from playhouse.migrate import *
+
+from server.models import db, Report
+from server.tools import UTC_now
+
+
+def run_migration():
+    if type(db) == peewee.SqliteDatabase:
+        migrator = SqliteMigrator(db)
+    elif type(db) == peewee.MySQLDatabase:
+        migrator = MySQLMigrator(db)
+    elif type(db) == peewee.PostgresqlDatabase:
+        migrator = PostgresqlMigrator(db)
+    else:
+        return
+
+    migrate(
+        migrator.add_column('report', 'first_report_datetime',
+                            peewee.DateTimeField(default=UTC_now)),
+    )
+    query = Report.select()
+    for report in query:
+        report.first_report_datetime = report.datetime
+        report.save()
+
+
+if __name__ == '__main__':
+    db.connect()
+    run_migration()
diff --git a/server/models.py b/server/models.py
index bf1b4b6..458f9ca 100644
--- a/server/models.py
+++ b/server/models.py
@@ -5,12 +5,13 @@ Models and database definition
 """
 import os
 
-import arrow
 import bottle
 import peewee
 from playhouse.db_url import connect
 from playhouse.shortcuts import model_to_dict
 
+from server.tools import UTC_now
+
 db = connect(os.environ.get('DATABASE', 'sqlite:///reports.db'))
 
 
@@ -40,8 +41,11 @@ class Report(BaseModel):
     type = peewee.CharField(max_length=255)
     lat = peewee.DoubleField()
     lng = peewee.DoubleField()
+    first_report_datetime = peewee.DateTimeField(
+        default=UTC_now
+    )
     datetime = peewee.DateTimeField(
-        default=lambda: arrow.utcnow().replace(microsecond=0).naive
+        default=UTC_now
     )
     expiration_datetime = peewee.DateTimeField(null=True)
     is_open = peewee.BooleanField(default=True)
diff --git a/server/routes.py b/server/routes.py
index 2eb4554..44c36d2 100644
--- a/server/routes.py
+++ b/server/routes.py
@@ -10,6 +10,7 @@ import os
 import bottle
 
 from server.models import Report
+from server.tools import UTC_now
 from server import jsonapi
 
 
@@ -80,7 +81,7 @@ def get_reports(only_active=False):
     if only_active:
         query = query.where(
             (Report.expiration_datetime == None) |
-            (Report.expiration_datetime > arrow.utcnow().replace(microsecond=0).datetime)
+            (Report.expiration_datetime > UTC_now())
         )
     query = query.order_by(*sorting)
     if page_number and page_size:
@@ -195,7 +196,7 @@ def post_report():
         # Handle expiration
         if r.type in ['accident', 'gcum']:
             r.expiration_datetime = (
-                arrow.utcnow().replace(microsecond=0).shift(hours=+1).datetime
+                arrow.get(UTC_now()).shift(hours=+1).naive
             )
         r.save()
     except KeyError as exc:
@@ -228,7 +229,15 @@ def upvote_report(id):
     r = Report.get(Report.id == id)
     if not r:
         return jsonapi.JsonApiError(404, "Invalid report id.")
+    # Increase upvotes
     r.upvotes += 1
+    # Update report datetime
+    r.datetime = UTC_now()
+    # Update expiration datetime
+    if r.type in ['accident', 'gcum']:
+        r.expiration_datetime = (
+            arrow.get(UTC_now()).shift(hours=+1).naive
+        )
     r.save()
 
     return {
@@ -282,7 +291,7 @@ def get_stats():
     nb_reports = Report.select().count()
     nb_active_reports = Report.select().where(
         (Report.expiration_datetime == None) |
-        (Report.expiration_datetime > arrow.utcnow().replace(microsecond=0).datetime)
+        (Report.expiration_datetime > UTC_now())
     ).count()
     last_added_report_datetime = Report.select().order_by(
         Report.datetime.desc()
diff --git a/server/tools.py b/server/tools.py
new file mode 100644
index 0000000..d925e6a
--- /dev/null
+++ b/server/tools.py
@@ -0,0 +1,5 @@
+import arrow
+
+
+def UTC_now():
+    return arrow.utcnow().replace(microsecond=0).naive
diff --git a/src/constants.js b/src/constants.js
index a6e861f..04228f4 100644
--- a/src/constants.js
+++ b/src/constants.js
@@ -85,8 +85,8 @@ export const MOCK_LOCATION_LNG_MAX = 2.392742;
 
 export const UPDATE_REPORTS_DISTANCE_THRESHOLD = 500; // in meters
 
-// Minimal ratio between upvotes and downvotes needed for a report to be shown
-export const REPORT_VOTES_THRESHOLD = 0.5;
+// Minimal number of downvotes needed for a report to be masked
+export const REPORT_DOWNVOTES_THRESHOLD = 1;
 
 export const EARTH_RADIUS = 6378137; // in meters
 
diff --git a/src/store/getters.js b/src/store/getters.js
index 0e99404..89131bb 100644
--- a/src/store/getters.js
+++ b/src/store/getters.js
@@ -1,4 +1,4 @@
-import { REPORT_VOTES_THRESHOLD } from '@/constants';
+import { REPORT_DOWNVOTES_THRESHOLD } from '@/constants';
 
 export function getLastLocation(state) {
     const { gpx } = state.location;
@@ -10,9 +10,9 @@ export function getLastLocation(state) {
 
 export function notDismissedReports(state) {
     return state.reports.filter((item) => {
-        if (item.attributes.downvotes === 0) {
-            return true;
+        if (item.attributes.downvotes >= REPORT_DOWNVOTES_THRESHOLD) {
+            return false;
         }
-        return (item.attributes.upvotes / item.attributes.downvotes) > REPORT_VOTES_THRESHOLD;
+        return true;
     });
 }