How can I change the format of the "upper" xAxis Label as shown in the picture?
I have already figured out how to change the weekday labels below (T, W, T, etc.) with the following snippet (for weeks, code placed within the xAxis):
dateTimeLabelFormats: {
week: {
list: ['Kalenderwoche %W', 'KW%W']
}
},
Existing example to play around: https://jsfiddle.net/gh/get/library/pure/highcharts/highcharts/tree/master/samples/gantt/demo/resource-management