Newsletter - Sendy "Too Busy Right Now" concept
Here's the concept of the "Too busy right now" feature:
The user will subscribe to your list with their email while passing in their email and timezone data into your backend script.
In the backend script, you need to calculate the reminder date based on what they selected in the 'X days' drop down menu and with respect to their timezone.
Once the 'Reminder Date' is calculated, send their email, 'Reminder Date' and 'Days to remind (eg. 5 days)' to your Sendy installation via the API.
The autoresponder you've created previously will send the reminder email based on the 'Reminder Date'. In the email body, you can include the personalization tag, 'Days to remind' [Daystoremind,fallback="few days ago"] so that you can say something like 'You wanted us to remind you to come back 5 days ago.'.