This is a Huawei firmware bug introduced with EMUI 8 and already reported in late 2017 (still unfixed by Huawei).
Previous workarounds relied on Android compatibility modes (pre-Oreo) which can no longer be published on Google Play.
This bug affects all scrollable widgets and is not a bug in aCalendar.
To have scrollable widgets properly updated on Huawei devices with this bug, aCalendar needs to run as service.
As background services are no longer allowed with Android 8, we provide a foreground service which also provides the current date in the status bar.
You can enable this as Sticky Date in notification settings.
We have a limited selection of Huawei devices and would be happy if you can provide feedback if this works - please use the THUMBS UP icon on this page to let us know if it works, use the THUMBS DOWN icon (and include details on device, Android version, EMUI version and widget used) if it doesn't.