I am uploading a NMU to fix this.
diff -Nru wmdate-0.7/debian/changelog wmdate-0.7/debian/changelog
--- wmdate-0.7/debian/changelog 2023-05-18 11:20:32.000000000 +0200
+++ wmdate-0.7/debian/changelog 2023-05-18 11:08:20.000000000 +0200
@@ -1,3 +1,11 @@
+wmdate (0.7-4.2) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * Update debhelper to level 7. Closes: #965879.
+ * Convert to source format 3.0 (quilt).
+
+ -- Bastian Germann <b...@debian.org> Thu, 18 May 2023 11:08:20 +0200
+
wmdate (0.7-4.1) unstable; urgency=medium
* Non-maintainer upload.
diff -Nru wmdate-0.7/debian/compat wmdate-0.7/debian/compat
--- wmdate-0.7/debian/compat 2023-05-18 11:20:32.000000000 +0200
+++ wmdate-0.7/debian/compat 2023-05-18 11:08:20.000000000 +0200
@@ -1 +1 @@
-6
+7
diff -Nru wmdate-0.7/debian/control wmdate-0.7/debian/control
--- wmdate-0.7/debian/control 2023-05-18 11:20:32.000000000 +0200
+++ wmdate-0.7/debian/control 2023-05-18 11:08:20.000000000 +0200
@@ -3,8 +3,8 @@
Priority: optional
Maintainer: Varun Hiremath <va...@debian.org>
Uploaders: Torsten Werner <twer...@debian.org>
-Build-Depends: debhelper (>= 6), cdbs, libdockapp-dev, xutils-dev, libx11-dev,
- libxext-dev, libxpm-dev, x11proto-core-dev, quilt
+Build-Depends: debhelper (>= 7), cdbs, libdockapp-dev, xutils-dev, libx11-dev,
+ libxext-dev, libxpm-dev, x11proto-core-dev
Standards-Version: 3.9.6
Homepage: http://solfertje.student.utwente.nl/~dalroi/wmdate/
Vcs-Svn: https://bollin.googlecode.com/svn/wmdate/trunk
diff -Nru wmdate-0.7/debian/rules wmdate-0.7/debian/rules
--- wmdate-0.7/debian/rules 2023-05-18 11:20:32.000000000 +0200
+++ wmdate-0.7/debian/rules 2023-05-18 11:08:20.000000000 +0200
@@ -2,7 +2,6 @@
include /usr/share/cdbs/1/rules/debhelper.mk
include /usr/share/cdbs/1/class/makefile.mk
-include /usr/share/cdbs/1/rules/patchsys-quilt.mk
DEB_MAKE_CLEAN_TARGET := distclean
DEB_MAKE_INSTALL_TARGET := install DESTDIR=$(CURDIR)/debian/wmdate
diff -Nru wmdate-0.7/debian/source/format wmdate-0.7/debian/source/format
--- wmdate-0.7/debian/source/format 1970-01-01 01:00:00.000000000 +0100
+++ wmdate-0.7/debian/source/format 2023-05-18 11:08:20.000000000 +0200
@@ -0,0 +1 @@
+3.0 (quilt)
