Empty date field becomes today's date
That happens because the date filter returns the current date for null values / empty strings.


  If the value passed to the date filter is null, it will return the current date by default.


To work around this, you would add a conditional.

{% if entry.myDate %}
    Date: {{ entry.myDate|date('Y-m-d') }}
{% endif %}


Another way to do this is to use a ternary operator.

{{ entry.myDate ? entry.myDate|date('Y-m-d') }}