diff --git a/README.md b/README.md
index 603a36b..dbe4fb0 100644
--- a/README.md
+++ b/README.md
@@ -16,4 +16,6 @@ optional arguments:
   -w N, --weekly N   keep N weekly backups, default: 4
   -m N, --monthly N  keep N monthly backups, default: 3
   -f, --force        suppress remove confirmation
+  -t FORMAT, --timestamp-format FORMAT
+                     format of timestamp, default: %Y%m%d
 ```
diff --git a/clean-backups.py b/clean-backups.py
index 77ddaaa..1379c24 100755
--- a/clean-backups.py
+++ b/clean-backups.py
@@ -8,6 +8,7 @@ import argparse
 DEFAULT_DAILY = 7
 DEFAULT_WEEKLY = 4
 DEFAULT_MONTHLY = 3
+DEFAULT_TIMESTAMP_FORMAT = "%Y%m%d"
 
 class BackupFile():
     """
@@ -168,6 +169,16 @@ parser.add_argument(
     action="store_true",
     help = "suppress remove confirmation"
 )
+# timestamp format
+parser.add_argument(
+    "-t",
+    "--timestamp-format",
+    type = str,
+    default = DEFAULT_TIMESTAMP_FORMAT,
+    metavar = "FORMAT",
+    help = f"format of timestamp, default: {DEFAULT_TIMESTAMP_FORMAT}".replace(r"%",r"%%")
+
+)
 args = parser.parse_args()
 
 daily = args.daily
@@ -175,9 +186,15 @@ weekly = args.weekly
 monthly = args.monthly
 force = args.force
 directory = args.path[0]
+timestamp_format = args.timestamp_format
 
 # File processing
-files = BackupFile(retention_daily = daily, retention_weekly = weekly, retention_monthly = monthly)
+files = BackupFile(
+    retention_daily = daily,
+    retention_weekly = weekly,
+    retention_monthly = monthly,
+    dateformat = timestamp_format
+)
 # Generate file list with full paths
 paths = [
     os.path.join(directory, f) for f in os.listdir(directory)
diff --git a/tests/filegenerator.py b/tests/filegenerator.py
index d1e6eb9..04f0f16 100755
--- a/tests/filegenerator.py
+++ b/tests/filegenerator.py
@@ -10,6 +10,7 @@ import os
 DEFAULT_NUMBER_OF_FILES = 200
 DEFAULT_PREFIX = "testfile-"
 DEFAULT_SUFFIX = ".bak"
+DEFAULT_TIMESTAMP_FORMAT = "%Y%m%d"
 
 # Argument parser
 parser = argparse.ArgumentParser(description="Cleanup old backups")
@@ -45,14 +46,26 @@ parser.add_argument(
     metavar = "SUFFIX",
     help = f"use SUFFIX as file name suffix, default: {DEFAULT_SUFFIX}"
 )
+# timestamp format
+parser.add_argument(
+    "-t",
+    "--timestamp-format",
+    type = str,
+    default = DEFAULT_TIMESTAMP_FORMAT,
+    metavar = "FORMAT",
+    help = f"format of timestamp, default: {DEFAULT_TIMESTAMP_FORMAT}".replace(r"%",r"%%")
+
+)
+
 args = parser.parse_args()
 path = args.path[0]
 number_of_files = args.number_of_files
 prefix = args.prefix
 suffix = args.suffix
+timestamp_format = args.timestamp_format
 
 for i in range(number_of_files):
-    timestamp = (date.today() - timedelta(days=i)).strftime("%Y%m%d")
+    timestamp = (date.today() - timedelta(days=i)).strftime(timestamp_format)
     filename = f"{prefix}{timestamp}{suffix}"
     Path(os.path.join(path, filename)).touch()
     
\ No newline at end of file