Zon = O.K. (short for “Zondag”)
Maandelijks should be “Ma” (short for “Maandag”)
Di = O.K. (short for “Dinsdag”)
Rood should be “Wo” (short for “Woensdag”)
Do = O.K. (short for “Donderdag”)
Vrienden should be “Vr” (short for “Vrijdag”)
Statistieken should be “Za” (short for “Zaterdag”)
I think it would be best to be consistent in number of characters when using abbreviations.
either [Zo,Ma,Di,Wo,Do,Vr,Za] or [Zon,Maa,Din,Woe,Don,vri,Zat]
