Invoice& quote date change doesn't work withIP is set to French

when IP is in English I can add a date to an invoice created from a quote ; when it’s in French IP is blocked with an error message. Same error when I want to change the date of a draft invoice.
I’ve upgraded to IP latest version but the bug is still there.

And what is the error message?

Here is a snapshot.

…did you even read the orange box on the top of this page? And the hints in the textfield for posting a support request?

Yes now I did and have put here the errors found in 3 logs (at least I hope these are the correct sources to track down the problem).


There is an error with the date function. Which date format did you set in the settings?

It’s 14-Aug-2017

I’ve just got this error page when trying to generate invoiceplane/index.php/reports/sales_by_client with date format 14-Aug-2017 :

Fatal error: Call to a member function format() on boolean in /srv/data/web/vhosts/ on line 115
A PHP Error was encountered
Severity: Error
Message: Call to a member function format() on boolean
Filename: helpers/date_helper.php
Line Number: 115

with date format set as 01.08.2017 the report generates OK.

Hope this help.