Fix date formatting in graph tooltips

dashboard/src/components/GraphItem.vue

@@ -4,7 +4,7 @@
 import moment from 'moment-timezone';
 import { onMounted, onUnmounted, useTemplateRef, watch } from 'vue';
 import Chart from 'chart.js/auto';
-import { prettyDecimalSize, prettyLongDate, prettyShortDate } from '@cloudron/pankow/utils';
+import { prettyDecimalSize, formatDate } from '@cloudron/pankow/utils';
 import annotationPlugin from 'chartjs-plugin-annotation';
 
 Chart.register(annotationPlugin);
@@ -100,7 +100,7 @@ function createGraphOptions({ yscale, period, highMark }) {
       tooltip: {
         enabled: false,
         callbacks: { // passed as title,body to the tooltip renderer
-          title: (tooltipItem) => period.tooltipFormat === 'long' ? prettyLongDate(tooltipItem[0].raw.x) : prettyShortDate(tooltipItem[0].raw.x),
+          title: (tooltipItem) => formatDate(period.tooltipFormat, tooltipItem[0].raw.x),
           label: (tooltipItem) => {
             const datasetLabel = tooltipItem.chart.data.datasets[tooltipItem.datasetIndex].label;
             return `${datasetLabel}: <span>${yscale.ticks.callback(tooltipItem.raw.y)}</span>`;