diff --git a/src/core/devices/nm-device.c b/src/core/devices/nm-device.c
index e882970479..a8a5285d1f 100644
--- a/src/core/devices/nm-device.c
+++ b/src/core/devices/nm-device.c
@@ -1294,7 +1294,7 @@ _prop_get_ipv6_dhcp_duid(NMDevice     *self,
             gint64  time;
             guint32 timestamp;
 
-#define EPOCH_DATETIME_THREE_YEARS (356 * 24 * 3600 * 3)
+#define EPOCH_DATETIME_THREE_YEARS (365 * 24 * 3600 * 3)
 
             /* We want a variable time between the host_id timestamp and three years
              * before. Let's compute the time (in seconds) from 0 to 3 years; then we'll