Instructions
Switch off your DS and remove the Acekard from Slot-1 located at the top of your device.
Insert the card into your PC using a card reader and wait for the "AutoPlay" menu to appear. Click "Open folder to view files" to see the contents of the card.
Double-click the "_aio" folder and then double-click the "ui" folder. This will open up the user interface folder where all the themes, or "skins," are stored.
Navigate to a website that has free skins for the AKAIO custom firmware. Sites such as Acekard and NDSthemes have a wide selection from which to choose. Look at the theme previews to find a theme that has the kind of calendar that you want and then click the "Download" link.
Right click on the downloaded file and select "Copy." Right click anywhere inside the "ui" folder you have open and select "Paste." Right click on the downloaded file inside the "ui" folder and select "Extract here."
Remove your card from the card reader after the file has been extracted and insert it back into your DS. Turn on the DS and tap the "Start" button (depending on what theme you are using it will be on the bottom right-hand corner of the screen).
Tap "System Options" and then "Interface Themes." Select the skin you have downloaded from the list of available skins. Tap "Yes" to confirm your selection and the skin will change. The calendar used with the original theme will be changed to the one of your new skin.