--- a/Makefile	2020-12-24 10:31:25.512121789 +0000
--- b/Makefile	2020-12-24 10:34:04.153576326 +0000
@@ -1,5 +1,10 @@
 
-DATE=$(shell date +%Y-%m-%d)
+DATE_FMT = +%Y-%m-%d
+ifdef SOURCE_DATE_EPOCH
+    DATE ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || date -u "$(DATE_FMT)")
+else
+    DATE ?= $(shell date "$(DATE_FMT)")
+endif
 PACKAGE=mail-expire
 VERSION=$(shell head -n1 debian/changelog | cut -f2 -d'(' | cut -f1 -d')')