diff --git a/build.py b/build.py
index 31936b8e4..b4bbab5b2 100644
--- a/build.py
+++ b/build.py
@@ -23,7 +23,7 @@
 from vttmisc import tsi1, tsic
 
 VERSION_YEAR_MONTH = 2110
-VERSION_DAY = 15
+VERSION_DAY = 31
 OUTPUT_DIR = Path("build")
 OUTPUT_OTF_DIR = OUTPUT_DIR / "otf"
 OUTPUT_TTF_DIR = OUTPUT_DIR / "ttf"