diff --git a/gemfeed.py b/gemfeed.py
index 7143263..93d5886 100755
--- a/gemfeed.py
+++ b/gemfeed.py
@@ -50,7 +50,7 @@ def get_feed_title(directory):
             return extract_first_heading(index_file, default)
     return default
 
-def find_files(directory, n=10):
+def find_files(directory, time_func, n=10):
     """
     Return the n most recently created world readable files with extensions of
     .gmi or .gemini, as a list sorted from most to least recent.
@@ -63,7 +63,7 @@ def find_files(directory, n=10):
         if index in files:
             files.remove(index)
     files = [f for f in files if is_world_readable(f)]
-    files.sort(key=os.path.getctime, reverse=True)
+    files.sort(key=time_func, reverse=True)
     return files[0:n]
 
 def urljoin(base, url):
@@ -85,7 +85,7 @@ def urljoin(base, url):
     joined = joined._replace(scheme="gemini")
     return urllib.parse.urlunsplit(joined)
 
-def populate_entry_from_file(filename, base_url, entry):
+def populate_entry_from_file(filename, base_url, entry, time_func):
     """
     Set the id, title, updated and link attributes of the provided
     FeedGenerator entry object according the contents of the named
@@ -94,13 +94,13 @@ def populate_entry_from_file(filename, base_url, entry):
     url = urljoin(base_url, os.path.basename(filename))
     entry.guid(url)
     entry.link(href=url, rel="alternate")
-    updated = get_update_time(filename)
+    updated = get_update_time(filename, time_func)
     entry.updated(updated)
     default_title = os.path.splitext(os.path.basename(filename))[0]
     title = extract_first_heading(filename, default_title)
     entry.title(title)
 
-def get_update_time(filename):
+def get_update_time(filename, time_func):
     """
     Return an update time for a Gemini file.
 
@@ -115,11 +115,11 @@ def get_update_time(filename):
         date = basename[0:10] + " Z" # Add UTC marker
         return datetime.datetime.strptime(date, "%Y-%m-%d %z")
     else:
-        updated = os.path.getctime(filename)
+        updated = time_func(filename)
         return datetime.datetime.fromtimestamp(updated, tz=datetime.timezone.utc)
 
-def build_feed(directory, base_url, output="atom.xml", n=10, title="",
-        subtitle="", author="", email="", verbose=False):
+def build_feed(directory, time_func, base_url, output="atom.xml", n=10,
+        title="", subtitle="", author="", email="", verbose=False):
     """
     Build an Atom feed for all world readable Gemini files in the current
     directory, and write it to atom.xml.
@@ -150,14 +150,14 @@ def build_feed(directory, base_url, output="atom.xml", n=10, title="",
     feed.link(href=base_url, rel='alternate')
 
     # Add one entry per .gmi file
-    files = find_files(directory, n)
+    files = find_files(directory, time_func, n)
     if not files:
         if verbose:
             print("No world-readable Gemini content found! :(")
         return
     for n, filename in enumerate(files):
         entry = feed.add_entry()
-        populate_entry_from_file(filename, base_url, entry)
+        populate_entry_from_file(filename, base_url, entry, time_func)
         if n == 0:
             feed.updated(entry.updated())
         if verbose:
@@ -199,6 +199,8 @@ def main():
             help='feed subtitle')
     parser.add_argument('-t', '--title', dest='title', type=str,
             help='feed title')
+    parser.add_argument('--mtime', action="store_true",
+            help='Use file modification time, not file update time, in feeds')
     args = parser.parse_args()
 
     # Normalise base URL
@@ -212,8 +214,10 @@ def main():
         args.base_url += "/"
 
     # Build the feed
-    build_feed(args.directory, args.base_url, args.output, args.n, args.title,
-            args.subtitle, args.author, args.email, args.verbose)
+    time_function = os.path.getmtime if args.mtime else os.path.getctime
+    build_feed(args.directory, time_function, args.base_url, args.output,
+            args.n, args.title, args.subtitle, args.author, args.email,
+            args.verbose)
 
 if __name__ == "__main__":
     main()