The limitations of BusyBox's cron implementation when it comes to defining schedules crop up again and again e.g. #267 #185 #117

There seems to be a standalone apk package for cron https://pkgs.alpinelinux.org/package/edge/main/x86/apk-cron which seems lightweight enough to install it in the image if:

• it supports all syntax that is supported by BusyBox
• it adds missing features like \ or -

Since this the core feature of this image, possible incompatibilities should be scrutinized closely before actually implementing.