Highcharts will automatically try to find the best format for the current zoom-range. This is done if the xAxis has the type 'datetime'. Next the unit of the current zoom is calculated, it could be one of:
- second
- minute
- hour
- day
- week
- month
- year
This unit is then used find a format for the axis labels. The default patterns are:
second: '%H:%M:%S',
minute: '%H:%M',
hour: '%H:%M',
day: '%e. %b',
week: '%e. %b',
month: '%b \'%y',
year: '%Y'
If you want the day to be part of the “hour”-level labels you should change the dateTimeLabelFormats option for that level include %d or %e.
These are the available patters:
- %a: Short weekday, like ‘Mon’.
- %A: Long weekday, like ‘Monday’.
- %d: Two digit day of the month, 01 to 31.
- %e: Day of the month, 1 through 31.
- %b: Short month, like ‘Jan’.
- %B: Long month, like ‘January’.
- %m: Two digit month number, 01 through 12.
- %y: Two digits year, like 09 for 2009.
- %Y: Four digits year, like 2009.
- %H: Two digits hours in 24h format, 00 through 23.
- %I: Two digits hours in 12h format, 00 through 11.
- %l (Lower case L): Hours in 12h format, 1 through 11.
- %M: Two digits minutes, 00 through 59.
- %p: Upper case AM or PM.
- %P: Lower case AM or PM.
- %S: Two digits seconds, 00 through 59
http://api.highcharts.com/highcharts#xAxis.dateTimeLabelFormats