Hi @Anonymous,
According to your description, I created a flow likes below for your reference.
The flow is triggered by a Button, getting items from a list. In the list, there is column Date. Then adding a Condition to check if current date is 30 days from the date specified in the list.
In advanced mode, enter the following code:
@equals(formatDateTime(utcnow(), 'yyyy-MM-dd'), formatDateTime(addDays(items('Apply_to_each')?['Date'], 30), 'yyyy-MM-dd'))
You could also try to enter the code in basic mode. Be sure to enter the code under the Expression tab likes below.
Then when the button is clicked, items that meet the condition will be sent out from flow.


Please take a try with it on your side.
Best regards,
Mabel Mao