diff --git a/gunicorn/main.py b/gunicorn/main.py
index 8f1b4256..eebf5622 100644
--- a/gunicorn/main.py
+++ b/gunicorn/main.py
@@ -67,7 +67,7 @@ def configure_logging(opts):
     logger = logging.getLogger('gunicorn')
     logger.setLevel(loglevel)
     format = r"%(asctime)s [%(process)d] [%(levelname)s] %(message)s"
-    datefmt = r"%Y/%m/%d %H:%M:%S"
+    datefmt = r"%Y-%m-%d %H:%M:%S"
     for h in handlers:
         h.setFormatter(logging.Formatter(format, datefmt))
         logger.addHandler(h)