We are switching off article comments on this website. Read about the upcoming changes to Atlassian Documentation.
You can customise the time and date formats used throughout JIRA on the 'Look and Feel' page.
To change your date and time formats for 'Issues' (JIRA):
Please note, the date and time formats will apply to pages within 'Issues' (JIRA) only. They do not apply to the other applications, e.g. 'Wiki'.
Screenshot: Changing Date and Time Formats