Email reminder plugin

Hi, i’m hunting for some help for my hunt for a plugin.

I am looking for a simple email reminder plugin which is free.

I have found loads of appointment booking plugins etc. but not just a simple (not time slotted) email reminder.

I have downloaded a plugin called ‘Email Reminder’ which is perfect, only it sits in the back end. I need it to be for a visitor to go on to a page and find a form which asks for name, email and date.
Say they chose 4 November. Then an automatic email will be sent on the 4 November telling her, for example, she needs to groom her dog.
The email would always be the same, but the customer chooses the date and the email is automated.

Hoping that makes sense? does anyone have any ideas of an available plugin?

Many thanks,
Lou