I still believe that calendars are excellent marketing devices. Many people will swear that they only use their phone calendars, but, calendars are still highly used and functional. In the promotional products industry, we have several good resources to brand a customers logo on each page and end up so the calendar only ends up running about $1ea. Pretty good ROI if you ask me.
Since 99.999% of my customers have a personal relationship with me, I started designing and self-publishing through my trade printer my own calendar a few years ago. My cost ends up being more like $10ea but if I needed to charge a client, for all the labor and creative involved I would end up charging over $1500 for a 100 pc run.
Anyway...blah, blah, blah. BUT, when you see those cute little calendars at the UPS store, it would be easy to say...Oh, I can DIY, right? Sure, but, to make a professional calendar there is alot more involved.
I design mine from SCRATCH using Lightroom, Photoshop, Illustrator and ultimately putting together in InDesign. Ok, more blah, blah, blah.
BUT, what is most difficult is choosing images from the past year that can remain interesting for 30 days. That is hard. It is alot easier to have a single theme versus photography in general; especially when picking from your own images.
Here is my 2020 calendar that I mail out to my customers and then target publishers, interior designers, etc.