Here is a little guide to using the shell component to make an calendarmaker.
You can find the shell component in the utilities category.
The component needs the following permissions.
More info can be found in the docs.
The block i am going to use in this guide is this one
In the textbox you can put the command that you would normally put in your linux terminal.
So far the technical stuff. Now the fun stuff begins.
You could make an app that would produce an image with a calendar below it. You could share that with other users. So you would have to use an image picker and the componenttoimage extension from @Jerin_Jacob, an arrangement, a couple of buttons and a textbox to display the calendar. I didn’t make a complete app just want to spark your fantasy.
These are the blocks i used.
This could be the result of this.
Now the month and year were hardcoded but you could use textboxes to enter the month and year.
@juananton1991 made a topic on the appinventor community that made me think of making this guide. His extension is doing what the shell component does. In his topic you can find a lot of commands that you can use with his extension and with the shell component.
Have fun and show here what you have made if you tried the guide.