Summary

When I choose a date from the date picker, Issue Editor raises an error saying that date format is invalid.

Answer

Set the Date Picker and Date Time Picker to match the format in Jira (System > Look and feel and System > General configuration > Advanced Settings).

Example

System > Look and feel

Time Format

h:mm a

Day Format

EEEE h:mm a

Complete Date/Time Format

dd/MMM/yy h:mm a

Day/Month/Year Format

dd/MMM/yy

System > General configuration > Advanced Settings

jira.date.picker.java.format

d/MMM/yy

jira.date.picker.javascript.format

%e/%b/%y

jira.date.time.picker.java.format

dd/MMM/yy h:mm a

jira.date.time.picker.javascript.format

%e/%b/%y %I:%M %p