diff --git a/src/render.js b/src/render.js
index 60e83c0..3bbffe3 100644
--- a/src/render.js
+++ b/src/render.js
@@ -101,6 +101,7 @@ class Chart {
  * Draw days to show time
  */
 export function render_calendar(canvas, width, height, offset, data) {
+
     const margin = {
         top: 0,
         left: leftMargin,
@@ -120,7 +121,9 @@ export function render_calendar(canvas, width, height, offset, data) {
     let days = []
     const year = data.beginTime.getFullYear()
     const month = data.beginTime.getMonth()
-    for (var day = data.beginTime.getDate(); day <= data.endTime.getDate(); day++) {
+
+    const n_days = Math.ceil((data.endTime- data.beginTime) / (1000 * 60 * 60 * 24))
+    for (var day = data.beginTime.getDate(); day <= (data.beginTime.getDate() + n_days); day++) {
         const dayBegin = new Date(year, month, day, 0, 1, 0)
         const noon = new Date(year, month, day, 12, 0, 0)
         noons.push(noon)
@@ -183,7 +186,9 @@ export function render_nights(canvas, width, height, offset, data) {
 
     const year = data.beginTime.getFullYear()
     const month = data.beginTime.getMonth()
-    for (var day = data.beginTime.getDate(); day <= data.endTime.getDate(); day++) {
+
+    const n_days = Math.ceil((data.endTime- data.beginTime) / (1000 * 60 * 60 * 24))
+    for (var day = data.beginTime.getDate(); day <= (data.beginTime.getDate() + n_days); day++) {
         const midnight = new Date(year, month, day, 0, 0, 0)
         const sunEphem = SunCalc.getTimes(new Date(year, month, day, 12, 0, 0), lat, lon)
         draw_box(midnight, sunEphem.nauticalDawn, 'night')
@@ -223,7 +228,9 @@ export function render_astronomy(canvas, width, height, offset, data) {
     let sunData = []
     const year = data.beginTime.getFullYear()
     const month = data.beginTime.getMonth()
-    for (var day = data.beginTime.getDate(); day <= data.endTime.getDate(); day++) {
+
+    const n_days = Math.ceil((data.endTime- data.beginTime) / (1000 * 60 * 60 * 24))
+    for (var day = data.beginTime.getDate(); day <= (data.beginTime.getDate() + n_days); day++) {
         const midnight = new Date(year, month, day, 0, 0, 0)
 
         // Solar Ephemeris