I know there are other posts like this, but if enough people add to the pile, maybe Fitbit it will do something about it. The menstrual calendar UI is just really, really poorly done. The previous one was much better and far more intuitive.
The most egregious issue that stands out when comparing to the previous calendar is that you must view each month individually, rather than seeing a seamless calendar that shows the months joined up seamlessly in a scrolling format. I don't know what man made this design choice, but periods do not fall neatly into each month, especially if you have long periods. Knowing the first day of your previous period and counting days in between is so helpful. Having to bounce back and forth between calendar months to keep count of cycle days is incredibly obnoxious and cumbersome.
The icons are difficult to parse at first glance since the ovulation date icon is so noticeable, while the ring indicator on the current date is far more subtle. The calendar symbols also don't communicate what they mean through icons that make sense. Having a flower symbol above an ovulation date tells me exactly what it is. A big black circle that doesn't match the rest of the calendar makes me think it is today's date rather than part of the cycle. It is just bad UI and counter-intuitive.
The choice to have the days of the week at the bottom of the calendar (instead of at the top like literally any other calendar in common use) is quite franky baffling. Like...why? Why did anyone think this was even something that needed to be changed? Again, it's counter-intuitive to standard calendars.
Having a natural color gradation between your period and fertile days when they overlap is so much easier to read than the weird stripes they have now. It previously emphasized the nature of an imprecise biological function much better than the rigid display they have now.
Also, the color palette is ugly. There, I said it. A minor note, I know, but it really just looks ugly and non-cohesive from a design standpoint.
This has whole thing has bugged me for a long time, and I'm finally remembering to make a complaint about it. If it ain't broke, don't fix it. The newer calendar is just a giant downgrade from the previous one.
