Calendar showing twice september with iphone

Hi all,

We are experiencing the following issue:

Region: Switzerland
Device: Iphone
Year: 1996 and previous years
Month: October

If all the above criteria are met, than the month september will be shown twice. So september will be shown instead of october. But when selecting a day, then october will be shown as month in the input field.

If we are in month september everything is correct (see September selection in the attached picture)

If we click next to proceed to month october, the month name is still “September”. But when selecting a day, then the date will be picked correctly showing october as month (see October selection in the attached picture)

We already tried to to define monthNames when creating the calendar, but still the same issue.
With all iphone devices (older and newer ones) we experience the same issue. No issue with android or with desktop browser.

We have a simple implementation of framework 7 calendar, without any customization:

First of all, how long do you estimate for providing us a fix for this issue? As our mobile web application is in use at lots of customer, we need a solution as soon as possible!

Thank you for looking into it and for a quick feedback.

Cheers from Switzerland