There are two ways to enter a date.
The first is by clicking the calendar icon, navigating to the correct year and month, then clicking the date. This is gone for revent dates, but more time consuming when deeper in the past.
The second method is to manually enter, but it is specifically in the below format:
DAY MONTH FULL-YEAR (example 25 Dec 2021 would be Christmas Day in 2021)
The day is the day number of the month. The month is first three letter if the month. The year (and this us most important) is all 4 digits. if you only use the last two digits, you will be off by 19 or 20 centuries when dates are use to calculate ages.