diff --git a/build.sh b/build.sh
index 66b5f9e88c0..ab07218a9be 100755
--- a/build.sh
+++ b/build.sh
@@ -198,7 +198,7 @@ function build_kernel() {
 }
 
 function build_android() {
-	true ${BUILD_NUMBER:=$(date +"6%y%m%d")$(($(date +"%H")/4))}
+	true ${BUILD_NUMBER:=$(date +"6%y%m%d")$(($(date +"%k")/4))}
 	export BUILD_NUMBER
 
 	FA_RunCmd lunch ${PRODUCT}-${VARIANT}