If you need to create some design for Calendars, while we waiting for Isaac implement this option for generate grids for calendars I share to you my solution for the moment.
1.You can create a grid via a file "Excel" setting the page for an A4 landscape for exemple, one section by month and export section by section on pdf, go to the tab Acrobat on the top and export pdf. (you find in attachement the Excel file for exemple, in french^^)
2. Then go to photoshop or other for open the pdf and save in a png. After that you've your grid in a png file, you can create a serie of grids in black color and an other serie with the text color white (if you your customer put a black background is better to have the same grid with white text color etc...)
3. Import your png file on Pitch Print Picture, on one categroy named "Grid of Calendard" for exemple.
4. After you can make an empty design where the client put himself the grid etc... or create some templates where you put yourself the grid. You can see in attachement an exemple of render mixed with the design selector module.
Of course that we'll be more simple when the new feature of pitch print will be here but for the moment it's a way for do that yourself.