diff --git a/jrnl/journals/FolderJournal.py b/jrnl/journals/FolderJournal.py
index c6faf1e02..018b2cebc 100644
--- a/jrnl/journals/FolderJournal.py
+++ b/jrnl/journals/FolderJournal.py
@@ -4,6 +4,7 @@
 import codecs
 import os
 import pathlib
+import re
 from typing import TYPE_CHECKING
 
 from jrnl import time
@@ -17,7 +18,6 @@
 DIGIT_PATTERN = "[0123456789]"
 YEAR_PATTERN = DIGIT_PATTERN * 4
 MONTH_PATTERN = "[01]" + DIGIT_PATTERN
-DAY_PATTERN = "[0123]" + DIGIT_PATTERN + ".txt"
 
 
 class Folder(Journal):
@@ -34,7 +34,7 @@ def open(self) -> "Folder":
         self.entries = []
 
         if os.path.exists(self.config["journal"]):
-            filenames = Folder._get_files(self.config["journal"])
+            filenames = Folder._get_files(self, self.config["journal"])
             for filename in filenames:
                 with codecs.open(filename, "r", "utf-8") as f:
                     journal = f.read()
@@ -45,6 +45,8 @@ def open(self) -> "Folder":
 
     def write(self) -> None:
         """Writes only the entries that have been modified into proper files."""
+        if self.config["extension"] is not None:
+            EXTENSION = self.config["extension"]
         # Create a list of dates of modified entries. Start with diff_entry_dates
         modified_dates = self._diff_entry_dates
         seen_dates = set(self._diff_entry_dates)
@@ -63,7 +65,7 @@ def write(self) -> None:
                 self.config["journal"],
                 d.strftime("%Y"),
                 d.strftime("%m"),
-                d.strftime("%d") + ".txt",
+                d.strftime("%d") + "." + EXTENSION,
             )
             dirname = os.path.dirname(filename)
             # create directory if it doesn't exist
@@ -81,7 +83,7 @@ def write(self) -> None:
                 journal_file.write(journal)
         # look for and delete empty files
         filenames = []
-        filenames = Folder._get_files(self.config["journal"])
+        filenames = Folder._get_files(self, self.config["journal"])
         for filename in filenames:
             if os.stat(filename).st_size <= 0:
                 os.remove(filename)
@@ -121,12 +123,14 @@ def parse_editable_str(self, edited: str) -> None:
         self.entries = mod_entries
 
     @staticmethod
-    def _get_files(journal_path: str) -> list[str]:
+    def _get_files(self, journal_path: str) -> list[str]:
         """Searches through sub directories starting with journal_path and find all text
         files that look like entries"""
+        if self.config["extension"] is not None:
+            EXTENSION = self.config["extension"]
         for year_folder in Folder._get_year_folders(pathlib.Path(journal_path)):
             for month_folder in Folder._get_month_folders(year_folder):
-                yield from Folder._get_day_files(month_folder)
+                yield from Folder._get_day_files(self, EXTENSION, month_folder)
 
     @staticmethod
     def _get_year_folders(path: pathlib.Path) -> list[pathlib.Path]:
@@ -143,10 +147,14 @@ def _get_month_folders(path: pathlib.Path) -> list[pathlib.Path]:
         return
 
     @staticmethod
-    def _get_day_files(path: pathlib.Path) -> list[str]:
-        for child in path.glob(DAY_PATTERN):
+    def _get_day_files(self, extension, path: pathlib.Path) -> list[str]:
+        EXTENSION = extension
+        DAY_PATTERN = "[0-3][0-9]." + EXTENSION
+        for child in path.iterdir():
+            match = re.fullmatch(DAY_PATTERN, str(child.name))
             if (
-                int(child.stem) > 0
+                match is not None
+                and int(child.stem) > 0
                 and int(child.stem) <= 31
                 and time.is_valid_date(
                     year=int(path.parent.name),