No, Marvin doesn't have Gantt charts. Marvin is built for personal planning rather than team project timelines, so this has not been prioritized ( But there are several ways to plan projects over weeks and months and see when you'll work on what.
Plan projects for a week, month or quarter
With Planning Ahead you can plan tasks and projects for a specific week, month or quarter. Press P to open the planner and switch between the week, month and quarter views. This gives you a rough timeline of what you want to tackle when, and helps you spread your projects out. See Planning Ahead and Capacity planning for weeks, months and quarters.
Give projects a start and an end
Start Dates: hide a project or task until the day you want to start it.
End Dates: set when you want to be finished.
Due dates (deadlines): the date something must be done by. A project's deadline is shown on its tasks too.
Put your work in order
Dependencies: a task waits until another task is done.
Sequential Projects: only the next task in a project shows, so you work through it step by step.
See your weeks
Week Scheduler: drag tasks onto the days of the week.
Calendar: see your tasks, events and time blocks on a calendar.
If a Gantt chart is important to you, let us know, so we can see how many people would use it.