diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/ChangeGroupingDialog.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/ChangeGroupingDialog.kt
index b477b8501..71da2f57d 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/ChangeGroupingDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/dialogs/ChangeGroupingDialog.kt
@@ -41,8 +41,10 @@ class ChangeGroupingDialog(val activity: BaseSimpleActivity, val path: String =
 
         val groupBtn = when {
             currGrouping and GROUP_BY_NONE != 0 -> groupingRadio.grouping_dialog_radio_none
-            currGrouping and GROUP_BY_LAST_MODIFIED_DAILY != 0 -> groupingRadio.grouping_dialog_radio_last_modified
-            currGrouping and GROUP_BY_DATE_TAKEN_DAILY != 0 -> groupingRadio.grouping_dialog_radio_date_taken
+            currGrouping and GROUP_BY_LAST_MODIFIED_DAILY != 0 -> groupingRadio.grouping_dialog_radio_last_modified_daily
+            currGrouping and GROUP_BY_LAST_MODIFIED_MONTHLY != 0 -> groupingRadio.grouping_dialog_radio_last_modified_monthly
+            currGrouping and GROUP_BY_DATE_TAKEN_DAILY != 0 -> groupingRadio.grouping_dialog_radio_date_taken_daily
+            currGrouping and GROUP_BY_DATE_TAKEN_MONTHLY != 0 -> groupingRadio.grouping_dialog_radio_date_taken_monthly
             currGrouping and GROUP_BY_FILE_TYPE != 0 -> groupingRadio.grouping_dialog_radio_file_type
             currGrouping and GROUP_BY_EXTENSION != 0 -> groupingRadio.grouping_dialog_radio_extension
             else -> groupingRadio.grouping_dialog_radio_folder
@@ -64,8 +66,10 @@ class ChangeGroupingDialog(val activity: BaseSimpleActivity, val path: String =
         val groupingRadio = view.grouping_dialog_radio_grouping
         var grouping = when (groupingRadio.checkedRadioButtonId) {
             R.id.grouping_dialog_radio_none -> GROUP_BY_NONE
-            R.id.grouping_dialog_radio_last_modified -> GROUP_BY_LAST_MODIFIED_DAILY
-            R.id.grouping_dialog_radio_date_taken -> GROUP_BY_DATE_TAKEN_DAILY
+            R.id.grouping_dialog_radio_last_modified_daily -> GROUP_BY_LAST_MODIFIED_DAILY
+            R.id.grouping_dialog_radio_last_modified_monthly -> GROUP_BY_LAST_MODIFIED_MONTHLY
+            R.id.grouping_dialog_radio_date_taken_daily -> GROUP_BY_DATE_TAKEN_DAILY
+            R.id.grouping_dialog_radio_date_taken_monthly -> GROUP_BY_DATE_TAKEN_MONTHLY
             R.id.grouping_dialog_radio_file_type -> GROUP_BY_FILE_TYPE
             R.id.grouping_dialog_radio_extension -> GROUP_BY_EXTENSION
             else -> GROUP_BY_FOLDER
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/helpers/MediaFetcher.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/helpers/MediaFetcher.kt
index a7f867c7b..a67a88468 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/helpers/MediaFetcher.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/helpers/MediaFetcher.kt
@@ -336,7 +336,8 @@ class MediaFetcher(val context: Context) {
         }
 
         val sortDescending = currentGrouping and GROUP_DESCENDING != 0
-        val sorted = if (currentGrouping and GROUP_BY_DATE_TAKEN_DAILY != 0 || currentGrouping and GROUP_BY_LAST_MODIFIED_DAILY != 0) {
+        val sorted = if (currentGrouping and GROUP_BY_LAST_MODIFIED_DAILY != 0 || currentGrouping and GROUP_BY_LAST_MODIFIED_MONTHLY != 0 ||
+                currentGrouping and GROUP_BY_DATE_TAKEN_DAILY != 0 || currentGrouping and GROUP_BY_DATE_TAKEN_MONTHLY != 0) {
             mediumGroups.toSortedMap(if (sortDescending) compareByDescending {
                 it.toLongOrNull() ?: 0L
             } else {
@@ -351,8 +352,8 @@ class MediaFetcher(val context: Context) {
             mediumGroups[key] = value
         }
 
-        val today = formatDate(System.currentTimeMillis().toString())
-        val yesterday = formatDate((System.currentTimeMillis() - DAY_SECONDS * 1000).toString())
+        val today = formatDate(System.currentTimeMillis().toString(), true)
+        val yesterday = formatDate((System.currentTimeMillis() - DAY_SECONDS * 1000).toString(), true)
         for ((key, value) in mediumGroups) {
             val sectionKey = getFormattedKey(key, currentGrouping, today, yesterday)
             thumbnailItems.add(ThumbnailSection(sectionKey))
@@ -363,13 +364,20 @@ class MediaFetcher(val context: Context) {
     }
 
     private fun getFormattedKey(key: String, grouping: Int, today: String, yesterday: String): String {
-        return when {
-            grouping and GROUP_BY_LAST_MODIFIED_DAILY != 0 || grouping and GROUP_BY_DATE_TAKEN_DAILY != 0 -> getFinalDate(formatDate(key), today, yesterday)
+        var result = when {
+            grouping and GROUP_BY_LAST_MODIFIED_DAILY != 0 || grouping and GROUP_BY_DATE_TAKEN_DAILY != 0 -> getFinalDate(formatDate(key, true), today, yesterday)
+            grouping and GROUP_BY_LAST_MODIFIED_MONTHLY != 0 || grouping and GROUP_BY_DATE_TAKEN_MONTHLY != 0 -> formatDate(key, false)
             grouping and GROUP_BY_FILE_TYPE != 0 -> getFileTypeString(key)
             grouping and GROUP_BY_EXTENSION != 0 -> key.toUpperCase()
             grouping and GROUP_BY_FOLDER != 0 -> context.humanizePath(key)
             else -> key
         }
+
+        if (result.isEmpty()) {
+            result = context.getString(R.string.unknown)
+        }
+
+        return result
     }
 
     private fun getFinalDate(date: String, today: String, yesterday: String): String {
@@ -380,11 +388,12 @@ class MediaFetcher(val context: Context) {
         }
     }
 
-    private fun formatDate(timestamp: String): String {
+    private fun formatDate(timestamp: String, showDay: Boolean): String {
         return if (timestamp.areDigitsOnly()) {
             val cal = Calendar.getInstance(Locale.ENGLISH)
             cal.timeInMillis = timestamp.toLong()
-            DateFormat.format("dd MMM yyyy", cal).toString()
+            val format = if (showDay) "dd MMM yyyy" else "MMM yyyy"
+            DateFormat.format(format, cal).toString()
         } else {
             ""
         }
diff --git a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/models/Medium.kt b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/models/Medium.kt
index 6be0459e9..6044219d7 100644
--- a/app/src/main/kotlin/com/simplemobiletools/gallery/pro/models/Medium.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/gallery/pro/models/Medium.kt
@@ -56,8 +56,10 @@ data class Medium(
 
     fun getGroupingKey(groupBy: Int): String {
         return when {
-            groupBy and GROUP_BY_LAST_MODIFIED_DAILY != 0 -> getDayStartTS(modified)
-            groupBy and GROUP_BY_DATE_TAKEN_DAILY != 0 -> getDayStartTS(taken)
+            groupBy and GROUP_BY_LAST_MODIFIED_DAILY != 0 -> getDayStartTS(modified, false)
+            groupBy and GROUP_BY_LAST_MODIFIED_MONTHLY != 0 -> getDayStartTS(modified, true)
+            groupBy and GROUP_BY_DATE_TAKEN_DAILY != 0 -> getDayStartTS(taken, false)
+            groupBy and GROUP_BY_DATE_TAKEN_MONTHLY != 0 -> getDayStartTS(taken, true)
             groupBy and GROUP_BY_FILE_TYPE != 0 -> type.toString()
             groupBy and GROUP_BY_EXTENSION != 0 -> name.getFilenameExtension().toLowerCase()
             groupBy and GROUP_BY_FOLDER != 0 -> parentPath
@@ -67,13 +69,17 @@ data class Medium(
 
     fun getIsInRecycleBin() = deletedTS != 0L
 
-    private fun getDayStartTS(ts: Long): String {
+    private fun getDayStartTS(ts: Long, resetDays: Boolean): String {
         val calendar = Calendar.getInstance(Locale.ENGLISH).apply {
             timeInMillis = ts
             set(Calendar.HOUR_OF_DAY, 0)
             set(Calendar.MINUTE, 0)
             set(Calendar.SECOND, 0)
             set(Calendar.MILLISECOND, 0)
+
+            if (resetDays) {
+                set(Calendar.DAY_OF_MONTH, 1)
+            }
         }
 
         return calendar.timeInMillis.toString()
diff --git a/app/src/main/res/layout/dialog_change_grouping.xml b/app/src/main/res/layout/dialog_change_grouping.xml
index a51c19111..c64aad625 100644
--- a/app/src/main/res/layout/dialog_change_grouping.xml
+++ b/app/src/main/res/layout/dialog_change_grouping.xml
@@ -29,20 +29,36 @@
                 android:text="@string/do_not_group_files"/>
 
             <com.simplemobiletools.commons.views.MyCompatRadioButton
-                android:id="@+id/grouping_dialog_radio_last_modified"
+                android:id="@+id/grouping_dialog_radio_last_modified_daily"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:paddingTop="@dimen/medium_margin"
                 android:paddingBottom="@dimen/medium_margin"
-                android:text="@string/by_last_modified"/>
+                android:text="@string/by_last_modified_daily"/>
 
             <com.simplemobiletools.commons.views.MyCompatRadioButton
-                android:id="@+id/grouping_dialog_radio_date_taken"
+                android:id="@+id/grouping_dialog_radio_last_modified_monthly"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:paddingTop="@dimen/medium_margin"
                 android:paddingBottom="@dimen/medium_margin"
-                android:text="@string/by_date_taken"/>
+                android:text="@string/by_last_modified_monthly"/>
+
+            <com.simplemobiletools.commons.views.MyCompatRadioButton
+                android:id="@+id/grouping_dialog_radio_date_taken_daily"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:paddingTop="@dimen/medium_margin"
+                android:paddingBottom="@dimen/medium_margin"
+                android:text="@string/by_date_taken_daily"/>
+
+            <com.simplemobiletools.commons.views.MyCompatRadioButton
+                android:id="@+id/grouping_dialog_radio_date_taken_monthly"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:paddingTop="@dimen/medium_margin"
+                android:paddingBottom="@dimen/medium_margin"
+                android:text="@string/by_date_taken_monthly"/>
 
             <com.simplemobiletools.commons.views.MyCompatRadioButton
                 android:id="@+id/grouping_dialog_radio_file_type"