Would you consider adding the month initial letter to the 1st date of that month? The additional character should be easy to fit into the presentation, and would make it far easier to track!
EDIT: I actually updated it to omit the day when it's the first day of the month. So instead of A1, it's just A. In the visual progression, seeing "A" seems to be enough to imply "we're now in August (1st)", and it's a little less visually cluttered when quickly scanning. Hopefully it's still clear, happy to adjust!
Added: https://github.com/hoffa/year-on-a-page/blob/main/renders/20...
EDIT: I actually updated it to omit the day when it's the first day of the month. So instead of A1, it's just A. In the visual progression, seeing "A" seems to be enough to imply "we're now in August (1st)", and it's a little less visually cluttered when quickly scanning. Hopefully it's still clear, happy to adjust!