Jira - date error when starting a Sprint - How to fix

Anyone who uses Jira from Atlassian may already know the problem: when starting a new sprint (see Screen 1) the error "... is not a valid date" appears, although the date corresponds to the specified format (and was even specified by Jira).

The change from the standard period to another predefined period also does not improve, since Jira always formats the date itself and the same error then occurs.

Even the change to a user-defined period fails if a period is selected that also fits the periods offered by Jira (Jira matches the select value and formats accordingly).

Workaround

The trick is simple: just add a space after the erroneous date field. Voila!