Currently we are allowing the user to write the date in whatever format they want. Unless they guess the format from the very beginning, an error is immediately prompted (see screen).

Formats vary very differently between countries, for example in the US it's common to use MM/DD/YYYY, whereas in other European countries they use DD.MM.YYYY.
Either provide a date picker that allows the user to select a date, or provide a UX that holds the hand of the user while typing the date. It doesn't have to be super complex, just something that points the user whether it starts with year, month or day (see example).
