Give an indication on the expected date format when input is wrong

Related to WCAG 2.1 criteria:

• level A criteria 1.4.1: use of color
• level AA criteria 3.3.3: error suggestion

When using a date picker and inputting a date in the wrong format manually, no indication is given on how it is supposed to be written. The only clue being given is that the label color changes to red, which also breaks the use of color criteria since a color blind user wouldn't notice it.

Expected: add an helper text that explains the error and how to solve it.