A denim jacket is also useful with this look, it helps extend its wear beyond the traditional seasons and is a useful dressing down piece. The stiff material means gives a bit of solidity that can be emphasized, giving new meaning to double denim, or softened with a more fluid fabric.
Going by these layering developments we’ll probably be seeing layered skirts next, I mean Phoebe’s already suggested as much...
and I may already have worn two denim skirts atop each other, completely unintended, just forgot to take one off when deciding between the two and being too lazy to take one off, so to save me from further embarrassment I've decided it's a thing now 
DAY 13 - DAY 13 - DAY 13 - DAY 13