diff --git a/read_mattermost.py b/read_mattermost.py
index 94825cd..0ae8ace 100755
--- a/read_mattermost.py
+++ b/read_mattermost.py
@@ -14,8 +14,6 @@ SERVER = "mattermost.zeus.gent"
 TEAM_NAME = "zeus"
 CHAN_NAME = "pannenkoeken"
 EMOJI_NAME = "pancakes"
-SINCE = datetime.datetime.strptime("2020-11-01 00:00", "%Y-%m-%d %H:%M") \
-	.astimezone(datetime.timezone.utc)
 TAGGERS = [
 	# Board
 	"flynn",
@@ -36,30 +34,25 @@ USER = os.getenv("MM_USERNAME")
 PASSWORD = os.getenv("MM_PASSWORD")
 
 
+try:
+	since_arg_i = sys.argv.index("--since")
+except ValueError:
+	SINCE = datetime.datetime.now(tz=datetime.timezone.utc)
+	print(f"Warning: no start time provided, using now. Use `--since {SINCE.isoformat(timespec='seconds')}` to pin the start time.", file=sys.stderr)
+if since_arg_i:
+	SINCE = datetime.datetime.fromisoformat(sys.argv[since_arg_i + 1])
+
+
+if sys.stdout.isatty():
+	print("To use this data, redirect stdout to a file and use table.py on it.", file=sys.stderr)
+
+
 def first(iterable, default=None):
 	for x in iterable:
 		return x
 	return default
 
 
-def get_posts_for_channel(mmapi, channel_id, since, **kwargs):
-	after = None
-	while True:
-		data_page = mmapi._get("/v4/channels/"+channel_id+"/posts", params=(
-			{ "after": after }
-			if after else
-			{ "since": to_mm_timestamp(since) }
-		), **kwargs)
-
-		order = list(reversed(data_page["order"]))
-		for post_id in order:
-			yield data_page["posts"][post_id]
-
-		if not order:
-			return
-		after = order[-1]
-
-
 ##################################
 # Log in
 mm = mattermost.MMApi(f"https://{SERVER}/api")
@@ -160,6 +153,24 @@ def retract_if_appropriate(reaction):
 	print(f"{awardee} {post['id']} verification removed by {awarder}", flush=True)
 
 
+def get_posts_for_channel(mmapi, channel_id, since, **kwargs):
+	after = None
+	while True:
+		data_page = mmapi._get("/v4/channels/"+channel_id+"/posts", params=(
+			{ "after": after }
+			if after else
+			{ "since": to_mm_timestamp(since) }
+		), **kwargs)
+
+		order = list(reversed(data_page["order"]))
+		for post_id in order:
+			yield data_page["posts"][post_id]
+
+		if not order:
+			return
+		after = order[-1]
+
+
 def handle_backlog(since):
 	for post in get_posts_for_channel(mm, channel, since):
 		for reaction in post.get("metadata", {}).get("reactions", []):
@@ -186,9 +197,6 @@ live = "--live" in sys.argv[1:]
 # Note: skipping this step and updating an existing file would be dangerous: you would miss revocations that happened while not listening.
 handle_backlog(SINCE)
 
-if sys.stdout.isatty():
-	print("To use this data, redirect stdout to a file and use make_table.py on it.", file=sys.stderr)
-
 if live:
 	print("Now watching for live posts.", file=sys.stderr)
 	handle_live()