bug build x axis using getTimezoneOffset

[hugomrdias]

When building the x axis, getTimezoneOffset method is called with a strange timestamp, but when building datalabels or tooltips everything seems ok.

example for DST change in 'Europe/Lisbon':
http://jsbin.com/seralet/14/edit?js,console

problem:
x axis has day 25 twice and tooltips and datalabels show the correct datetime

[TorsteinHonsi]

What happens is that the tick for the 26th is actually placed one hour too early (24h after the last tick), so the date becomes wrong. You see that clearly from this screenshot. Also note that both the tick placement and the point placement is correct, the only problem is that we would expect the tick to be at midnight.

[VilmaRamos]

Now the result is as I was expecting but trying to achieve the same result using only the pointStart and pointInterval properties didn't work. The following example illustrates the problem: http://jsbin.com/tojakel/2/edit?html,js,output .
Is it possible to define the point intervals using an irregular time interval? Maybe something like:

series: {
    pointStart: 1445641200000,
    pointInterval: 1,
    pointIntervalUnit: 'day'
}

[TorsteinHonsi]

Good point! The current defination of pointIntervalUnit only covers month and year, but in order to cover DST crossover it should also cover day.

[TorsteinHonsi]

Since it is unrelated to the axis label placement, I added an issue at #4958.

[pawelfus]

It's still a little buggy: http://jsfiddle.net/1mtv71bx/

On the xAxis we can see 6. Nov twice: once at 00:00 and later at 23:00. All next daily higherRanks are translated by 1h to the left.

[TorsteinHonsi]

Internal note
The problem lies in these lines that don't take into consideration that the axis can cross over DST even if the interval is smaller than days and weeks.

We need a separate clause below the day/week clause, that applies to hours and less. If the minDate and max lies in different time zones, we need to compute the time using makeTime like higher order times. Pseudo code, in real implementation we need to replace hours, possibly day, and minutes to support half-hour time zones:

var crossingDST = getTZOffset(minDate) !== getTZOffset(max);
[...]
            // if we're using global time, the interval is not fixed as it jumps
            // one hour at the DST crossover
            } else if (variableDayLength && (interval === timeUnits.day || interval === timeUnits.week)) {
                time = makeTime(minYear, minMonth, minDateDate +
                    i * count * (interval === timeUnits.day ? 1 : 7));

            } else if (variableDayLength && crossingDST) {
                time = makeTime(minYear, minMonth, day, hour, minute, second);
            }