This reverts commit fcc123bb1b.

src/backend/model/database/SearchManager.ts

@@ -779,7 +779,7 @@ export class SearchManager {
                 break;
 
               case DatePatternFrequency.months_ago:
-                to.setUTCMonth(to.getUTCMonth() - tq.agoNumber);
+                to.setTime(Utils.addMonthToDate(to, -1 * tq.agoNumber).getTime());
                 break;
 
               case DatePatternFrequency.years_ago:

src/common/Utils.ts

@@ -220,6 +220,19 @@ export class Utils {
     return dayOfYear;
   }
 
+  //Adding months to a date differently from standard JS
+  //this function makes sure that if date is the 31st and you add a month, you will get the last day of the next month
+  //so adding or subtracting a month from 31st of march will give 30th of april or 28th of february respectively (29th on leap years).
+  static addMonthToDate(date: Date, numMonths: number) {
+    const result = new Date(date)
+    const expectedMonth = ((date.getMonth() + numMonths) % 12 + 12) % 12; //inner %12 + 12 makes correct handling of negative months
+    result.setMonth(result.getMonth() + numMonths);
+    if (result.getMonth() !== expectedMonth) {
+      result.setDate(0);
+    }
+    return result;
+  }
+
   static renderDataSize(size: number): string {
     const postFixes = ['B', 'KB', 'MB', 'GB', 'TB'];
     let index = 0;

test/backend/unit/model/sql/SearchManager.spec.ts

@@ -132,18 +132,9 @@ describe('SearchManager', (sqlHelper: DBTestHelper) => {
     delete pFaceLessTmp.metadata.faces;
     d = new Date();
     //we create a date 1 month and 1 day before now
-    if ([1, 3, 5, 7, 8, 10, 0].includes(d.getMonth())) {
-      //Now is a month after a long month: feb (1), april (3), june (5), august(7), september(8), november (10), january (0)
-      pFaceLessTmp.metadata.creationDate = d.getTime() - 60 * 60 * 24 * 32 * 1000;
-    } else if (d.getMonth() == 2 && Utils.isDateFromLeapYear(d)) {
-      //march on leap years
-      pFaceLessTmp.metadata.creationDate = d.getTime() - 60 * 60 * 24 * 30 * 1000;
-    } else if (d.getMonth() == 2) {
-      //march (and not leap years)
-      pFaceLessTmp.metadata.creationDate = d.getTime() - 60 * 60 * 24 * 29 * 1000;
-    } else { //all other months must come after a short month with 30 days, so we subtract 31
-      pFaceLessTmp.metadata.creationDate = d.getTime() - 60 * 60 * 24 * 31 * 1000;
-    }
+    d = Utils.addMonthToDate(d, -1); //subtract 1 month in the "human way"
+    d.setDate(d.getDate()-1); //subtract 1 day
+    pFaceLessTmp.metadata.creationDate = d.getTime();
     pFaceLessTmp.metadata.creationDateOffset = "+02:00";
 
     dir = await DBTestHelper.persistTestDir(directory);