Marcel,

You can use the toUTCString() method to convert Javascript timestamp values into UTC format. Please refer to this stack overflow thread for more information.

Also, you can use the toLocaleString() method in labelFormatter and tooltip contentFormatter to format date-time values displayed in the axis labels and tooltip. You can output dates that are in UTC or local time to a specific timezone by passing timeZone option to toLocaleString().

—
Thangaraj Raman
Team CanvasJS