From c3a880e5f53df5dcb1e068f2a8bce6ff6594de39 Mon Sep 17 00:00:00 2001
From: MaysWind <i@mayswind.net>
Date: Tue, 5 Nov 2024 00:55:22 +0800
Subject: [PATCH] keep the day of the month when shifting the date range
 forward or backward if the selected date range is a full month

---
 src/lib/datetime.js | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/lib/datetime.js b/src/lib/datetime.js
index 88f43a40..cc36825a 100644
--- a/src/lib/datetime.js
+++ b/src/lib/datetime.js
@@ -355,6 +355,7 @@ export function getShiftedDateRange(minTime, maxTime, scale) {
     const firstDayOfMonth = minDateTime.clone().startOf('month');
     const lastDayOfMonth = maxDateTime.clone().endOf('month');
 
+    // check whether the date range matches full months
     if (firstDayOfMonth.unix() === minDateTime.unix() && lastDayOfMonth.unix() === maxDateTime.unix()) {
         const months = getYear(maxDateTime) * 12 + getMonth(maxDateTime) - getYear(minDateTime) * 12 - getMonth(minDateTime) + 1;
         const newMinDateTime = minDateTime.add(months * scale, 'months');
@@ -366,6 +367,18 @@ export function getShiftedDateRange(minTime, maxTime, scale) {
         };
     }
 
+    // check whether the date range matches one full month
+    if (minDateTime.clone().add(1, 'months').subtract(1, 'seconds').unix() === maxDateTime.unix() ||
+        maxDateTime.clone().subtract(1, 'months').add(1, 'seconds').unix() === minDateTime.unix()) {
+        const newMinDateTime = minDateTime.add(1 * scale, 'months');
+        const newMaxDateTime = maxDateTime.add(1 * scale, 'months');
+
+        return {
+            minTime: newMinDateTime.unix(),
+            maxTime: newMaxDateTime.unix()
+        };
+    }
+
     const range = (maxTime - minTime + 1) * scale;
 
     return {