Hi. Any kludge with Evernote would be just that: a workaround that's almost certainly more complicated than just using a link in Evernote to jump to and from a saved calendar in Sheet or elsewhere. I'm a strong believer in finding an app that deals most efficiently with an issue - like mind mapping or calendaring - and using that to process your data.
You could use an Evernote calendar template as a well-laid-out table of contents note and set up Filterize (or another automation app) to populate each day with any tasks tagged with that date, or with reminders due that day - in fact a note tagged <20200124> (or more efficiently <2020> <M01> <D24>) could appear in day, month and year templates for any given client, or for a group of clients. -The extreme case of a year display for all clients, potentially being a very large note indeed!