Thanks for quick reply.
Since it doesn’t look good enough yet to have it online I just took two screenshots of the calendar widget enabled, once with calendar appearance setting to light theme and once to dark theme. Actually the dark theme looks even lighter…
https://artservice.auroville.org/wp-content/uploads/2016/02/ScreenShot_calendar_light.png
https://artservice.auroville.org/wp-content/uploads/2016/02/ScreenShot_calendar_dark.png
Thanks for help