What I did:Fall in love with app on my iPad and told my husband i wanted to get an iMac
What happened:He bought me an early 2008 iMac
What I expected:that there might be an older app version
Things that might be helpful to know (Agenda version, OS and model, etc): are there any other apps or programs which work well with agenda so i can use my new iMac and not upset my husband
That’s awesome to hear that you like Agenda so much that you wanted a Mac to run it on it as well 
Agenda requires macOS 12 or higher, which was the actual OS version when we shipped the first version of Agenda back in 2018. Not sure if you’re Mac can be upgraded to macOS12 if it’s not running it at the moment?
Hi thanks for the response. I’ve been told that 'el capitan’, which is its current os is as high as it goes.
What would be helpful is to find out what other apps people use which work well with Agenda to keep me going until i can afford a newer mac
You can also try this software, which helps to install new macOS versions on old Macs that aren‘t supported officially by Apple. This way I was able to install macOS Mojave on my old MacbookPro from 2009 which isn‘t supported either.
Please work your way through the Readme‘s to make shure that your Mac is on the compatibility list.
http://dosdude1.com/software.html
It‘s a bit tricky though, and perhaps your graphic card doesn‘t support Metal — which will prevent you to work with software that rely on that.
But it‘s worth the effort: You would be able to work with Agenda 
Btw: Use at your own risk, make backups…