To add a restriction between the start and end date you can add a Validator in the workflow, then if the customer selects the start date 1/Aug/2019 the limit for end date will be 31/Jul/2020.
Please, go to the Project settings > Workflows > Select to edit the desired workflow > Select the diagram mode and select the "Create" transition.
On the next page, click on "Add validator" and choose the Date window validator > Add.
Select the fields to be validated the same as below:
After that, publish the workflow and it will start working for the future tickets.
The only problem for that is the message that will appear in the portal that will not show specifically what is the error but it will highlight the end date field, so my suggestion is that you add a message on the introduction of the project (Project settings > Portal settings > Introduction text) informing about the start and end date.
Hope this helps!
Thank you for reaching out to Community!
The steps I shared are valid only for Jira Cloud. Jira Server doesn’t have the same validators and post functions and most of them are based on add-ons.
I found only one thread here in the community with a similar request that may help you:
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