diff --git a/apps/dav/lib/CalDAV/BirthdayService.php b/apps/dav/lib/CalDAV/BirthdayService.php
index e1e46316d74fa..799f8610703e9 100644
--- a/apps/dav/lib/CalDAV/BirthdayService.php
+++ b/apps/dav/lib/CalDAV/BirthdayService.php
@@ -187,9 +187,9 @@ public function buildDateFromContact(string $cardData,
 			$originalYear = (int)$dateParts['year'];
 		}
 
-		$leapDay = ((int)$dateParts['month'] === 2
-				&& (int)$dateParts['date'] === 29);
-		if ($dateParts['year'] === null || $originalYear < 1970) {
+		$leapDay = ((int)$dateParts['month'] === 2 && (int)$dateParts['date'] === 29);
+
+		if ($dateParts['year'] === null) {
 			$birthday = ($leapDay ? '1972-' : '1970-')
 				. $dateParts['month'] . '-' . $dateParts['date'];
 		}
diff --git a/apps/dav/tests/unit/CardDAV/BirthdayServiceTest.php b/apps/dav/tests/unit/CardDAV/BirthdayServiceTest.php
index aeee04fd6eee8..42cf87f64b6f8 100644
--- a/apps/dav/tests/unit/CardDAV/BirthdayServiceTest.php
+++ b/apps/dav/tests/unit/CardDAV/BirthdayServiceTest.php
@@ -397,31 +397,31 @@ public function providesVCards() {
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:someday\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
-			['🎂 12345 (1900)', '19700101', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19000101\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
-			['🎂 12345 (1900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
-			['Death of 12345 (1900)', '19701231', 'FREQ=YEARLY', 'DEATHDATE', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nDEATHDATE:19001231\r\nEND:VCARD\r\n", 'DEATHDATE', '-death', true, null],
-			['Death of 12345 (1900)', '19701231', 'FREQ=YEARLY', 'DEATHDATE', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nDEATHDATE:19001231\r\nEND:VCARD\r\n", 'DEATHDATE', '-death', false, null],
-			['💍 12345 (1900)', '19701231', 'FREQ=YEARLY', 'ANNIVERSARY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nANNIVERSARY:19001231\r\nEND:VCARD\r\n", 'ANNIVERSARY', '-anniversary', true, null],
-			['12345 (⚭1900)', '19701231', 'FREQ=YEARLY', 'ANNIVERSARY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nANNIVERSARY:19001231\r\nEND:VCARD\r\n", 'ANNIVERSARY', '-anniversary', false, null],
+			['🎂 12345 (1900)', '19000101', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19000101\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
+			['🎂 12345 (1900)', '19001231', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
+			['Death of 12345 (1900)', '19001231', 'FREQ=YEARLY', 'DEATHDATE', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nDEATHDATE:19001231\r\nEND:VCARD\r\n", 'DEATHDATE', '-death', true, null],
+			['Death of 12345 (1900)', '19001231', 'FREQ=YEARLY', 'DEATHDATE', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nDEATHDATE:19001231\r\nEND:VCARD\r\n", 'DEATHDATE', '-death', false, null],
+			['💍 12345 (1900)', '19001231', 'FREQ=YEARLY', 'ANNIVERSARY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nANNIVERSARY:19001231\r\nEND:VCARD\r\n", 'ANNIVERSARY', '-anniversary', true, null],
+			['12345 (⚭1900)', '19001231', 'FREQ=YEARLY', 'ANNIVERSARY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nANNIVERSARY:19001231\r\nEND:VCARD\r\n", 'ANNIVERSARY', '-anniversary', false, null],
 			['🎂 12345', '19701231', 'FREQ=YEARLY', 'BDAY', '1', null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:--1231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			['🎂 12345', '19701231', 'FREQ=YEARLY', 'BDAY', '1', null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY;X-APPLE-OMIT-YEAR=1604:16041231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:;VALUE=text:circa 1800\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nN:12345;;;;\r\nBDAY:20031231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
-			['🎂 12345 (900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:09001231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
-			['12345 (*1900)', '19700101', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19000101\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
-			['12345 (*1900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
+			['🎂 12345 (900)', '09001231', 'FREQ=YEARLY', 'BDAY', '0', '900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:09001231\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
+			['12345 (*1900)', '19000101', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19000101\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
+			['12345 (*1900)', '19001231', 'FREQ=YEARLY', 'BDAY', '0', '1900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
 			['12345 *', '19701231', 'FREQ=YEARLY', 'BDAY', '1', null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:--1231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
 			['12345 *', '19701231', 'FREQ=YEARLY', 'BDAY', '1', null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY;X-APPLE-OMIT-YEAR=1604:16041231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:;VALUE=text:circa 1800\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nN:12345;;;;\r\nBDAY:20031231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
-			['12345 (*900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:09001231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
-			['12345 (*1900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '1900', 'PT9H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, 'PT9H'],
-			['12345 (*1900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '1900', '-PT15H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, '-PT15H'],
-			['12345 (*1900)', '19701231', 'FREQ=YEARLY', 'BDAY', '0', '1900', '-P6DT15H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, '-P6DT15H'],
+			['12345 (*900)', '09001231', 'FREQ=YEARLY', 'BDAY', '0', '900', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:09001231\r\nEND:VCARD\r\n", 'BDAY', '', false, null],
+			['12345 (*1900)', '19001231', 'FREQ=YEARLY', 'BDAY', '0', '1900', 'PT9H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, 'PT9H'],
+			['12345 (*1900)', '19001231', 'FREQ=YEARLY', 'BDAY', '0', '1900', '-PT15H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, '-PT15H'],
+			['12345 (*1900)', '19001231', 'FREQ=YEARLY', 'BDAY', '0', '1900', '-P6DT15H', "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19001231\r\nEND:VCARD\r\n", 'BDAY', '', false, '-P6DT15H'],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19000101\r\nX-NC-EXCLUDE-FROM-BIRTHDAY-CALENDAR;TYPE=boolean:true\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nX-NC-EXCLUDE-FROM-BIRTHDAY-CALENDAR;TYPE=boolean:true\r\nDEATHDATE:19001231\r\nEND:VCARD\r\n", 'DEATHDATE', '-death', true, null],
 			[null, null, null, null, null, null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nANNIVERSARY:19001231\r\nX-NC-EXCLUDE-FROM-BIRTHDAY-CALENDAR;TYPE=boolean:true\r\nEND:VCARD\r\n", 'ANNIVERSARY', '-anniversary', true, null],
-			['🎂 12345 (1902)', '19720229', 'FREQ=YEARLY;BYMONTH=2;BYMONTHDAY=-1', 'BDAY', '0', null, null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19020229\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
+			['🎂 12345 (1904)', '19040229', 'FREQ=YEARLY;BYMONTH=2;BYMONTHDAY=-1', 'BDAY', '0', '1904', null, "BEGIN:VCARD\r\nVERSION:3.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nUID:12345\r\nFN:12345\r\nN:12345;;;;\r\nBDAY:19040229\r\nEND:VCARD\r\n", 'BDAY', '', true, null],
 		];
 	}
 }