Not sure if you are using Jira Cloud or not, but assuming you are, then using Automation would be the way to do this.
Setup a rule along the lines of:
Trigger = Field value changed (field being fix version), on edit and create.
Condition = When Fix version is not empty
Action = Edit issue (and set up the relevant date fields as follows)
Hi everyone, We’re always looking at how to improve Confluence and customer feedback plays an important role in making sure we're investing in the areas that will bring the most value to the most c...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events