Extract datestamps from filename if possible.

gemfeed.py

@@ -4,6 +4,7 @@ import datetime
 import glob
 import os
 import os.path
+import re
 import stat
 import urllib.parse
 
@@ -93,13 +94,30 @@ 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 = os.path.getctime(filename)
-    updated = datetime.datetime.fromtimestamp(updated, tz=datetime.timezone.utc)
+    updated = get_update_time(filename)
     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):
+    """
+    Return an update time for a Gemini file.
+
+    If the filename begins with an ISO8601 date stamp, that date
+    (with a time of midnight) will be used.  Otherwise, the file
+    "creation time" (which in unix is actually the time of last
+    metadata update) will be used instead as a best estimate.
+    """
+    # Check for leading YYYY-MM-DD
+    basename = os.path.basename(filename)
+    if re.search("^[0-9]{4}-[01][0-9]-[0-3][0-9]", basename):
+        date = basename[0:10] + " Z" # Add UTC marker
+        return datetime.datetime.strptime(date, "%Y-%m-%d %z")
+    else:
+        updated = os.path.getctime(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):
     """