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After you created a plan it’s possible to edit its details. You can change its name and duration, but remember that tasks that will fall outside of the new range will be either removed or shortened to the new range.
To edit the plan you need to be either a Jira admin or a creator of this plan.
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To edit a plan you first need to open this plan page. There you will find an Edit details button.
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Click it and a modal will show up.
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Here you can change the plan name.
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The main project can not be changed after you created a plan. You can still however add issues from other projects.
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The plan duration can be changed either by selecting a predefined duration or manually selecting the start and end date. Please remember that if you had tasks already added to the plan and they will not fit into the new duration then they will be removed which is not reversible.
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After you are done with your changes you can press the Save changes button to save the changes.