Hello!

The screenshot from macOS 12.0.1 (Monterey) shows in foreground at the top GNU Emacs 29.0.50 (built in MacPorts) and in foreground at the bottom GNU Emacs 28.0.90 (built manually with MacPorts' Clang 13) and in-between in background GNU Emacs 28.0.50 (built manually with Clang 11 in an older version of macOS, 11.X, Big Sur) which has a correct mode-line. The other two versions display in calendar mode-line a white background where the command options '?', 'o' or '.' are shown. (GNU Emacsen 28.0.X use a "germanised" version of calendar.)

The question is whether it's the source code or it's the macOS version that produces the faults…