Using a catalog to populate a push based on date

Try using code snippet like below:

{% capture currentDate %}
    {{ "now" | time_zone: 'Australia/Sydney' | date: "%Y-%m-%d"  }}
{% endcapture %}
{% catalog_items my_catalog {{currentDate}} %}
{{items[0].preheader  }} 

This should work as we are using successfully.

Make sure to update the time_zone to your environment's timezone.