diff --git a/net-mgmt/thanos/Makefile b/net-mgmt/thanos/Makefile
index 8a4cab1af936..9c4f9f220f53 100644
--- a/net-mgmt/thanos/Makefile
+++ b/net-mgmt/thanos/Makefile
@@ -1,31 +1,31 @@
 PORTNAME=	thanos
 DISTVERSIONPREFIX=	v
 DISTVERSION=	0.41.0
 PORTREVISION=	5
 CATEGORIES=	net-mgmt
 
 MAINTAINER=	alven@FreeBSD.org
 COMMENT=	Highly available Prometheus setup with long term storage capabilities
 WWW=		https://thanos.io/ \
 		https://github.com/thanos-io/thanos/
 
 LICENSE=	APACHE20
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
 USES=		go:modules
 
 GO_MODULE=	github.com/thanos-io/thanos
 GO_TARGET=	./cmd/${PORTNAME}
 GO_BUILDFLAGS=	-tags slicelabels
 GO_LDFLAGS=	-X github.com/prometheus/common/version.Branch="master" \
 		-X github.com/prometheus/common/version.BuildDate=${BUILD_DATE} \
 		-X github.com/prometheus/common/version.BuildUser=${USER} \
 		-X github.com/prometheus/common/version.Revision=${REVISION} \
 		-X github.com/prometheus/common/version.Version=${DISTVERSION}
 
 PLIST_FILES=	bin/${PORTNAME}
 
-BUILD_DATE=	$$(date +%d-%B-%Y)
+BUILD_DATE=	${:Udate +%F:sh}
 REVISION=	cb1396b9
 
 .include <bsd.port.mk>