diff --git a/packages/mermaid/src/config.type.ts b/packages/mermaid/src/config.type.ts
index 0ba317868..2914a4606 100644
--- a/packages/mermaid/src/config.type.ts
+++ b/packages/mermaid/src/config.type.ts
@@ -1281,6 +1281,11 @@ export interface GanttDiagramConfig extends BaseDiagramConfig {
    *
    */
   weekday?: 'monday' | 'tuesday' | 'wednesday' | 'thursday' | 'friday' | 'saturday' | 'sunday';
+  /**
+   * On which day a weekend interval should start
+   *
+   */
+  weekend?: 'friday' | 'saturday';
 }
 /**
  * The object containing configurations specific for sequence diagrams
diff --git a/packages/mermaid/src/diagrams/gantt/ganttDb.js b/packages/mermaid/src/diagrams/gantt/ganttDb.js
index b0058ff8d..6d0c21b54 100644
--- a/packages/mermaid/src/diagrams/gantt/ganttDb.js
+++ b/packages/mermaid/src/diagrams/gantt/ganttDb.js
@@ -21,6 +21,7 @@ dayjs.extend(dayjsIsoWeek);
 dayjs.extend(dayjsCustomParseFormat);
 dayjs.extend(dayjsAdvancedFormat);
 
+const WEEKEND_START_DAY = { friday: 5, saturday: 6 };
 let dateFormat = '';
 let axisFormat = '';
 let tickInterval = undefined;
@@ -37,6 +38,7 @@ let funs = [];
 let inclusiveEndDates = false;
 let topAxis = false;
 let weekday = 'sunday';
+let weekend = 'saturday';
 
 // The serial order of the task in the script
 let lastOrder = 0;
@@ -63,6 +65,7 @@ export const clear = function () {
   links = {};
   commonClear();
   weekday = 'sunday';
+  weekend = 'saturday';
 };
 
 export const setAxisFormat = function (txt) {
@@ -167,7 +170,11 @@ export const isInvalidDate = function (date, dateFormat, excludes, includes) {
   if (includes.includes(date.format(dateFormat.trim()))) {
     return false;
   }
-  if (date.isoWeekday() >= 6 && excludes.includes('weekends')) {
+  if (
+    excludes.includes('weekends') &&
+    (date.isoWeekday() == WEEKEND_START_DAY[weekend] ||
+      date.isoWeekday() == WEEKEND_START_DAY[weekend] + 1)
+  ) {
     return true;
   }
   if (excludes.includes(date.format('dddd').toLowerCase())) {
@@ -184,6 +191,14 @@ export const getWeekday = function () {
   return weekday;
 };
 
+export const setWeekend = function (startDay) {
+  weekend = startDay;
+};
+
+export const getWeekend = function () {
+  return weekend;
+};
+
 /**
  * TODO: fully document what this function does and what types it accepts
  *
@@ -781,6 +796,8 @@ export default {
   isInvalidDate,
   setWeekday,
   getWeekday,
+  setWeekend,
+  getWeekend,
 };
 
 /**
diff --git a/packages/mermaid/src/diagrams/gantt/parser/gantt.jison b/packages/mermaid/src/diagrams/gantt/parser/gantt.jison
index d6027fee9..f2333ff84 100644
--- a/packages/mermaid/src/diagrams/gantt/parser/gantt.jison
+++ b/packages/mermaid/src/diagrams/gantt/parser/gantt.jison
@@ -84,6 +84,8 @@ weekday\s+thursday              return 'weekday_thursday'
 weekday\s+friday                return 'weekday_friday'
 weekday\s+saturday              return 'weekday_saturday'
 weekday\s+sunday                return 'weekday_sunday'
+weekend\s+friday                return 'weekend_friday'
+weekend\s+saturday              return 'weekend_saturday'
 \d\d\d\d"-"\d\d"-"\d\d          return 'date';
 "title"\s[^\n]+               return 'title';
 "accDescription"\s[^#\n;]+      return 'accDescription'
@@ -128,6 +130,11 @@ weekday
   | weekday_sunday { yy.setWeekday("sunday");}
   ;
 
+weekend
+  : weekend_friday { yy.setWeekend("friday");}
+  | weekend_saturday { yy.setWeekend("saturday");}
+  ;
+
 statement
   : dateFormat {yy.setDateFormat($1.substr(11));$$=$1.substr(11);}
   | inclusiveEndDates {yy.enableInclusiveEndDates();$$=$1.substr(18);}
@@ -138,6 +145,7 @@ statement
   | includes {yy.setIncludes($1.substr(9));$$=$1.substr(9);}
   | todayMarker {yy.setTodayMarker($1.substr(12));$$=$1.substr(12);}
   | weekday
+  | weekend
   | title {yy.setDiagramTitle($1.substr(6));$$=$1.substr(6);}
   | acc_title acc_title_value { $$=$2.trim();yy.setAccTitle($$); }
   | acc_descr acc_descr_value { $$=$2.trim();yy.setAccDescription($$); }