Trello and Google Calendar are two popular tools used for task management and time planning respectively, but they don't integrate seamlessly out of the box. To bridge this gap, users can set up a one-way integration that shows Trello cards with due dates in Google Calendar or use Zapier to create customizable integrations, allowing users to add Google Calendar appointments to Trello or control which Trello cards show up in Google Calendar. The iCal subscription feature in Trello allows for automatic syncing of calendar data with Google Calendar, but this is a static subscription that only works one way. Users can also build their own workflows using Zapier's automation tools to send information from one app to the other in various ways, such as creating new Trello cards from new Google Calendar events or deleting Trello cards when corresponding Google Calendar events are archived.