I am also running the newest CF 7 plugin version 4.2.2 and the newest wordpress version. I have the same problem with the datepicker format and also a date-range problem. If people on my site need to enter the expiry date of their ID-card it is not possible to select a future date from the calendar pop-up. However, if I than manually change the date (without the pop-up calendar) it is okay to have a future date and doesn’t resolve into an error or something. I hope to be able to add the proper date-format. Great plugin further on!!