What pattern should be applied when a table should be read vertically?

[Ennoriel]

Most tables can be read both horizontally and vertically. Though, it always conveys a different meaning. Most of the times, the expected reading direction is horizontal. However, sometimes the most ovious reading direction is vertically.

For example, I assume that the Github calendar graph shown below should be read vertically. When you read it horizontally, you get the contributions of the past 52 Sundays, then 52 Mondays, etc. That doesn't feel very convenient to understand.

Is there a way to convey this directionality?