diff --git a/generator/cli.py b/generator/cli.py
index 60888df..f4e8ea3 100644
--- a/generator/cli.py
+++ b/generator/cli.py
@@ -1,9 +1,28 @@
+import argparse
 from datetime import datetime, timedelta
 
 from generator import generate_changelog
 
 
+def parsed_date(s):
+    try:
+        return datetime.strptime(s, "%Y-%m-%d %H:%M:%S")
+    except ValueError:
+        msg = "Not a valid date: '{0}'.".format(s)
+        raise argparse.ArgumentTypeError(msg)
+
+
 def main():
     since = datetime.today() - timedelta(5)
 
-    generate_changelog(since)
+    parser = argparse.ArgumentParser(description='Generate changelogs from closed GitHub issues and merged PRs.')
+    parser.add_argument('--since', metavar='"YYYY-MM-DD HH:MM:SS"', type=parsed_date,
+                        help='date of previous release')
+    parser.add_argument('--output', metavar='"YYYY-MM-DD HH:MM:SS"', type=parsed_date,
+                        help='date of previous release')
+    group = parser.add_mutually_exclusive_group(required=True)
+    group.add_argument('--html', action='store_const', const="html", dest="output", help="output as HTML")
+    group.add_argument('--markdown', action='store_const', const="markdown", dest="output", help="output as markdown")
+
+    args = parser.parse_args()
+    generate_changelog(args.since, args.output)
diff --git a/generator/formatters/html.py b/generator/formatters/html.py
index 6b1e000..5255c26 100644
--- a/generator/formatters/html.py
+++ b/generator/formatters/html.py
@@ -9,7 +9,8 @@ class HTMLFormatter(BaseFormatter):
         text = "<div>\n"
         for repo in self.repos:
             if repo.issues:
-                text += "<h3><a href='{}'>{}</a></h3>\n".format(repo.absolute_url, repo.path)
+                if len(self.repos) > 1:
+                    text += "<h3><a href='{}'>{}</a></h3>\n".format(repo.absolute_url, repo.path)
                 text += "<ul>\n"
                 for issue in repo.issues:
                     text += "\t<li><a href='{url}'>#{id}</a> {title}".format(
diff --git a/generator/formatters/markdown.py b/generator/formatters/markdown.py
index 1c33c0b..22ca773 100644
--- a/generator/formatters/markdown.py
+++ b/generator/formatters/markdown.py
@@ -9,7 +9,8 @@ class MarkdownFormatter(BaseFormatter):
         text = ""
         for repo in self.repos:
             if repo.issues:
-                text += "### [{}]({})\n".format(repo.path, repo.absolute_url)
+                if len(self.repos) > 1:
+                    text += "### [{}]({})\n".format(repo.path, repo.absolute_url)
                 for issue in repo.issues:
                     text += "  - [#{id}]({url}) {title}".format(
                         url=issue.url,
diff --git a/generator/generator.py b/generator/generator.py
index bcd2651..836cca0 100644
--- a/generator/generator.py
+++ b/generator/generator.py
@@ -25,7 +25,7 @@ def generate_statistics(repos: List[Repo]):
     print("{num} Tickets closed by {contr} contributors".format(num=num_issues, contr=len(unique_authors)))
 
 
-def generate_changelog(since: datetime):
+def generate_changelog(since: datetime, output_format):
     repos = []
     for repo_url in config.repositories:
         repo = Repo(repo_url)
@@ -45,5 +45,10 @@ def generate_changelog(since: datetime):
         repo.issues = issues
         repos.append(repo)
 
-    print(HTMLFormatter(repos))
+    if output_format == "html":
+        print(HTMLFormatter(repos))
+    elif output_format == "markdown":
+        print(MarkdownFormatter(repos))
+    else:
+        raise ValueError()
     generate_statistics(repos)