If this is a topic you don't know much about but are willing to write on, send in a query to the editor and see if they have any specific stories they'd like to assign you. If you don't see an editorial calendar on the website then go ahead and inquire with the magazine - they probably have one they don't share, have not updated the latest calendar online, or have all their stories assigned and don't need more writers. Many magazines prepare for issues 3-6 months in advance so it might help to check with the editor which issue you can pitch for.
In my experience, working with an editorial calendar has been the best. If I am pitching to a new magazine, then I look for the calendar on their site. If I find it, then I write in to the editor highlighting the stories I'd be interested in and checking which months I should pitch for. If I don't find it, I write in asking if there is one and if it could be shared so I can pitch. I have never had someone reply saying no! Many magazines, especially the new up and coming ones, are always looking for writers and are very happy when you reach out to them for assignments.
That said, here are the links to editorial calendars for a few magazines. Maybe you will find some ideas here and an opportunity to write:
1. Buckhaven Lifestyle
2. Computer World
3. Architectural Record
5. Mother Earth News