Use Date.current and Time.current

Using Date.today and Time.now might lead to inconsistencies if the time
zone the application uses is not the same as the system time zone.

db/dev_seeds/newsletters.rb

@@ -17,7 +17,7 @@ section "Creating Newsletters" do
       segment_recipient: UserSegments::SEGMENTS.sample,
       from: "no-reply@consul.dev",
       body: newsletter_body.sample,
-      sent_at: [Time.now, nil].sample
+      sent_at: [Time.current, nil].sample
     )
   end
 end