Hi @Anonymous ,
Could you please share a bit more about your Calendar screen that you made?
Do you want to make your Calendar displayed in full screen?
If you wan to make your Calendar displayed in full screen, you could consider configure your app in a Tablet Layout, and then set the Width property of the Outer Calendar Gallery to following:
App.Width
You could consider configure your Calendar screen as a Responsive Layout screen, please refer to the following article:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/create-responsive-layout
If you want to display the corresponding events (from same SP Calendar List) for current day in your Sub Gallery, please consider set the Items property of the Sub Gallery (nested Gallery) to following:
Filter('Calendar List', DateValue(Text('Start Time')) = DateValue(Text(ThisItem.DateValue)))
Note: The DateValue represents the column value in your Outer Gallery, which display the date value. e.g. 2/27/2020, 2/28/2020, ....
In order to only display the Day value within your Outer Gallery, you could use the following formula:
Day(ThisItem.DateValue)
You also need to add a Timer control in your screen to refresh your Calendar List in a specific internals, e.g. refresh Calendar List data source every 5 seconds. Set the Duration property to following:
5000
set the AutoStart and Repeat property to following:
true
set the OnTimerEnd property to following:
Refresh('Calendar List')
Please consider take a try with above solution, check if the issue is solved.
Best regards,