diff --git a/app/assets/javascripts/visualisations/timeseries.ts b/app/assets/javascripts/visualisations/timeseries.ts
index e4cda2d2f8..d22fd6bac7 100644
--- a/app/assets/javascripts/visualisations/timeseries.ts
+++ b/app/assets/javascripts/visualisations/timeseries.ts
@@ -266,14 +266,14 @@ export class TimeseriesGraph extends SeriesExerciseGraph {
         } else if (this.binStep < 168) { // binning per multiple days
             const format = d3.timeFormat(i18n.t("date.formats.weekday_long"));
             message = `
-                <b>${format(d.date)} - ${format(new Date(d.date - this.binStep * 3600000))}:</b>
+                <b>${format(d.date)} - ${format(new Date(d.date + this.binStep * 3600000))}:</b>
                 <br>
             `;
         } else { // binning per week(s)
             const weekDay = d3.timeFormat(i18n.t("date.formats.weekday_long"));
             const monthDay = d3.timeFormat(i18n.t("date.formats.monthday_long"));
             message = `
-                <b>${weekDay(d.date)} - ${monthDay(new Date(d.date - this.binStep * 3600000))}:</b>
+                <b>${weekDay(d.date)} - ${monthDay(new Date(d.date + this.binStep * 3600000))}:</b>
                 <br>
             `;
         }