Symptoms

In JIRA when reviewing the Activity panel for an issue with logged time an invalid date is displayed:

Cause

JIRA Cloud 'Look and Feel' allows customization of 'Date/Time Formats'.  There are additional configuration items available for JIRA installed: Invalid date when trying to Log Work on Issue in JIRA  

Resolution

• Cog icon > System - User Interface > Look and Feel
• Bottom of the page has 'Date/Time Formats'
• Select 'Revert' to restore the previous settings or

• Edit the settings to match the Simple Date Link
  

  info is good