diff --git a/sources/container/qetzip.cpp b/sources/container/qetzip.cpp
index 7a0be3c26..dc9e2c9f7 100644
--- a/sources/container/qetzip.cpp
+++ b/sources/container/qetzip.cpp
@@ -22,6 +22,7 @@
 #include <QFile>
 #include <QSaveFile>
 #include <QSet>
+#include <QtEndian>
 
 namespace {
 void setError(QString *error, const QString &text)
@@ -44,6 +45,42 @@ bool safeName(const QString &name)
 	}
 	return true;
 }
+
+	//Built with MINIZ_NO_TIME, miniz leaves each entry's DOS date at 0,
+	//day 0 of month 0, which is no date: unzip shows 30 Nov 1979, other
+	//tools 13 Dec 1901. Give every entry 1 Jan 1980 00:00 instead, the
+	//first valid DOS date, so the bytes still do not depend on the time.
+constexpr quint16 EntryDosDate = (1 << 5) | 1;
+
+bool setEntryDates(QByteArray *bytes)
+{
+	char *data = bytes->data();
+	mz_zip_archive zip;
+	mz_zip_zero_struct(&zip);
+	if (!mz_zip_reader_init_mem(&zip, data, size_t(bytes->size()), 0)) return false;
+
+	bool ok = true;
+	const mz_uint count = mz_zip_reader_get_num_files(&zip);
+	for (mz_uint i = 0 ; i < count && ok ; ++i)
+	{
+		mz_zip_archive_file_stat stat;
+		if (!mz_zip_reader_file_stat(&zip, i, &stat)) {
+			ok = false;
+			break;
+		}
+			//date at offset 12 of the local header, 14 of the central one
+		const quint64 local = stat.m_local_header_ofs + 12;
+		const quint64 central = zip.m_central_directory_file_ofs + stat.m_central_dir_ofs + 14;
+		if (local + 2 > quint64(bytes->size()) || central + 2 > quint64(bytes->size())) {
+			ok = false;
+			break;
+		}
+		qToLittleEndian<quint16>(EntryDosDate, data + local);
+		qToLittleEndian<quint16>(EntryDosDate, data + central);
+	}
+	mz_zip_reader_end(&zip);
+	return ok;
+}
 }
 
 /**
@@ -87,8 +124,12 @@ QByteArray QetZip::toBytes(const QList<Entry> &entries, QString *error)
 		mz_zip_writer_end(&zip);
 		return {};
 	}
-	const QByteArray bytes(static_cast<const char *>(buffer), qsizetype(size));
+	QByteArray bytes(static_cast<const char *>(buffer), qsizetype(size));
 	mz_zip_writer_end(&zip);   //frees buffer
+	if (!setEntryDates(&bytes)) {
+		setError(error, QStringLiteral("cannot date the zip entries"));
+		return {};
+	}
 	return bytes;
 }
 
diff --git a/sources/container/qetzip.h b/sources/container/qetzip.h
index 9238f6ebf..808a861ce 100644
--- a/sources/container/qetzip.h
+++ b/sources/container/qetzip.h
@@ -30,8 +30,8 @@
 	megabytes, not gigabytes -- and written through QSaveFile, so a failed
 	save leaves the previous file as it was.
 
-	Entries carry no timestamp: saving the same project twice gives the
-	same bytes.
+	Every entry is dated 1 Jan 1980 00:00, not the time of saving: saving
+	the same project twice gives the same bytes.
 */
 namespace QetZip
 {
diff --git a/tests/qttest/tst_qetzip.cpp b/tests/qttest/tst_qetzip.cpp
index 4c69afef3..156cb8fb6 100644
--- a/tests/qttest/tst_qetzip.cpp
+++ b/tests/qttest/tst_qetzip.cpp
@@ -2,6 +2,7 @@
 #include <QtTest>
 
 #include <QTemporaryDir>
+#include <QtEndian>
 
 #include "container/qetzip.h"
 #include "container/miniz/miniz.h"
@@ -72,6 +73,33 @@ private slots:
 		QCOMPARE(QetZip::toBytes(sample()), QetZip::toBytes(sample()));
 	}
 
+	// every entry carries a valid date in both of its headers, not the
+	// 0 miniz writes without a clock (shown as 1979 or 1901 by unzip tools)
+	void entriesHaveValidDate()
+	{
+		const QByteArray zip = QetZip::toBytes(sample());
+		QVERIFY(!zip.isEmpty());
+		mz_zip_archive archive;
+		mz_zip_zero_struct(&archive);
+		QVERIFY(mz_zip_reader_init_mem(&archive, zip.constData(), size_t(zip.size()), 0));
+		const mz_uint count = mz_zip_reader_get_num_files(&archive);
+		QCOMPARE(int(count), sample().size());
+		for (mz_uint i = 0 ; i < count ; ++i) {
+			mz_zip_archive_file_stat stat;
+			QVERIFY(mz_zip_reader_file_stat(&archive, i, &stat));
+			const char *local = zip.constData() + stat.m_local_header_ofs;
+			const char *central = zip.constData() + archive.m_central_directory_file_ofs + stat.m_central_dir_ofs;
+			QCOMPARE(qFromLittleEndian<quint16>(local), quint16(0x50 | 0x4b << 8));   // "PK"
+			QCOMPARE(qFromLittleEndian<quint16>(central), quint16(0x50 | 0x4b << 8));
+			// 1 Jan 1980: day 1, month 1, year 0 since 1980; time 00:00:00
+			QCOMPARE(qFromLittleEndian<quint16>(local + 12), quint16(0x21));
+			QCOMPARE(qFromLittleEndian<quint16>(central + 14), quint16(0x21));
+			QCOMPARE(qFromLittleEndian<quint16>(local + 10), quint16(0));
+			QCOMPARE(qFromLittleEndian<quint16>(central + 12), quint16(0));
+		}
+		mz_zip_reader_end(&archive);
+	}
+
 	void refusesUnsafeNamesOnWrite_data()
 	{
 		QTest::addColumn<QString>("name");