Yes, I know “Ahead By A Century” is tuned in open C - capoed up to open D.
In my experience with alternate tunings, I found it was easier when I had more than one guitar and could leave a guitar in that tuning.
The tuner in Justin’s Song’s app does not support alternate tunings. I’m sure there are tuner apps that do, but I don’t have any experience. Search for “chromatic tuners”, or post a specific question (this has been asked here before, IIRC).