This is one of the few inventions I came up with on my own.
So, instead of ripping off the previous month's calendar and throwing it away, or using tape to tape up the subsequent month, what I currently do is to place two paperclips on both the top right and top left corners of the calendar (see red ovals in image below). That way, it's easier to flip to the next month in the calendar, while keeping the calendar relatively intact.