how to hide 'hour' in xAxis

how to hide 'hour' in xAxis

I have a line chart with xAxis as follows:
'xAxis' : {
'type' : 'datetime',
'labels' : {
'rotation' : -90,
'align' : 'right',
'y' : 1
},
'dateTimeLabelFormats' : {
'day' : '%e-%b',
'week' : '%e-%b',
'month' : '%b-%y'
}
}
But it shows not only day/month but also hours. Is there a way to hide
hours here?