Chris Winfield Co-Founder and CMO of BlueGlass Interactive, an Internet Marketing agency, stresses the importance of making your content relevant to the time of year at which you're providing it.
I think that this is one of the easiest ways to find inspiration for content marketing that most people overlook. Winfield addresses the concern of having "evergreen content," which works all of the time, no matter what. This sentiment is understandable, but I think that if you're creating this type of content it's less likely to be shared or valued as much as content that's relevant to something that's occurring right now.
Though it might take more time, it's important to find out what "National Day" it is (sort of), or to think about what's going on in the world that relates to your company when creating new content.