Highcharts DateTime Localization

Just to complete a little bit this topic:

All the options related with language are available here

A full Portuguese example:

var highchartsOptions = Highcharts.setOptions({
      lang: {
            loading: 'Aguarde...',
            months: ['Janeiro', 'Fevereiro', 'Março', 'Abril', 'Maio', 'Junho', 'Julho', 'Agosto', 'Setembro', 'Outubro', 'Novembro', 'Dezembro'],
            weekdays: ['Domingo', 'Segunda', 'Terça', 'Quarta', 'Quinta', 'Sexta', 'Sábado'],
            shortMonths: ['Jan', 'Feb', 'Mar', 'Abr', 'Maio', 'Jun', 'Jul', 'Ago', 'Set', 'Out', 'Nov', 'Dez'],
            exportButtonTitle: "Exportar",
            printButtonTitle: "Imprimir",
            rangeSelectorFrom: "De",
            rangeSelectorTo: "Até",
            rangeSelectorZoom: "Periodo",
            downloadPNG: 'Download imagem PNG',
            downloadJPEG: 'Download imagem JPEG',
            downloadPDF: 'Download documento PDF',
            downloadSVG: 'Download imagem SVG'
            // resetZoom: "Reset",
            // resetZoomTitle: "Reset,
            // thousandsSep: ".",
            // decimalPoint: ','
            }
      }
  );

To localize weekdays, Highcharts.setOptions should be called before chart creation and contain the new weekday names:

Highcharts.setOptions({
    lang: {
        weekdays: ['Dimanche', 'Lundi', 'Mardi', 'Mercredi', 'Jeudi', 'Vendredi', 'Samedi']
} });

Note that the array should start with the name for Sunday not Monday (the first day of the work week).

Example on jsFiddle

And in German (note though that the mini-buttons in Highstocks are still labeled "YTD","1y", and "All") :

Highcharts.setOptions({
                 lang: {
                     decimalPoint: ',',
                     thousandsSep: '.',
                     loading: 'Daten werden geladen...',
                     months: ['Januar', 'Februar', 'März', 'April', 'Mai', 'Juni', 'Juli', 'August', 'September', 'Oktober', 'November', 'Dezember'],
                     weekdays: ['Sonntag', 'Montag', 'Dienstag', 'Mittwoch', 'Donnerstag', 'Freitag', 'Samstag'],
                     shortMonths: ['Jan', 'Feb', 'Mär', 'Apr', 'Mai', 'Jun', 'Jul', 'Aug', 'Sep', 'Okt', 'Nov', 'Dez'],
                     exportButtonTitle: "Exportieren",
                     printButtonTitle: "Drucken",
                     rangeSelectorFrom: "Von",
                     rangeSelectorTo: "Bis",
                     rangeSelectorZoom: "Zeitraum",
                     downloadPNG: 'Download als PNG-Bild',
                     downloadJPEG: 'Download als JPEG-Bild',
                     downloadPDF: 'Download als PDF-Dokument',
                     downloadSVG: 'Download als SVG-Bild',
                     resetZoom: "Zoom zurücksetzen",
                     resetZoomTitle: "Zoom zurücksetzen"
                       }
});

To change the range selector buttons, some more information is needed:

rangeSelector: {
              buttons: [{
                  count: 1,
                  type: 'month',
                  text: '1M'
            }, {
                  count: 5,
                  type: 'month',
                  text: '5M'
            }, {
                  type: 'all',
                  text: 'Alles'
            }],
            inputEnabled: false,
            selected: 0
        },

month/months -> Monat/Monate  ("M" is the correct abbreviation)
minute/minutes-> Minute/Minuten
millisecond/milliseconds-> Millisekunde/Millisekunden
year/years -> Jahr/Jahre
all -> Alles (everything) or Gesamt (the whole)   
ytd (year to date) -> seit Jahresbeginn (since the start of this year)