Duoweek is a co-parenting app for separated parents that brings parenting schedules, shared child-related costs, and messages into one place. It is available for iPhone, Android, and the web. Parents can view a shared calendar showing who has each overnight, choose a starting date, and print a calendar to review together. Parents can propose changes to the schedule, such as swapping a weekend. The calendar updates only after the other parent approves the proposal, and the response is recorded with its date. For expenses, users can enter an amount, proposed split, and receipt if available. The other parent can agree, decline with a reason, or propose a different amount, subject to the rules and response deadline shown for the request. Messages are organized by topic and cannot be edited after they are sent. Users can mark messages for later reference. Proposals, responses, payments, and messages are dated and retained in a history that can be used to print a report of schedule changes, costs, and communications. To use the app together, one parent downloads Duoweek and invites the other parent, after which both can access the shared calendar, cost records, and messages.