We've made a couple of small visual improvements to the calendar as part of the gradual process of improvements on the page.
The header is lighter and the text has more space to sit in to improve legibility. Borders have been thinned to make them less dominating. A reminder of how it looked before:
And how it looks today:
Additionally, a small improvement was made to line up the horizontal lines between the columns that in some browsers were out by a single pixel.