diff --git a/server.js b/server.js
index f5335a6..fa104a1 100644
--- a/server.js
+++ b/server.js
@@ -319,10 +319,10 @@ export async function writeToMonica(entry) {
         is_deceased_date_known: false
       };
       if (bday.is_birthdate_known) {
-        postBody.day = bday.day;
-        postBody.month = bday.month;
+        postBody.birthdate_day = bday.day;
+        postBody.birthdate_month = bday.month;
         if (bday.year !== null) {
-          postBody.year = bday.year;
+          postBody.birthdate_year = bday.year;
         }
       }
       const newContactPayload = await monicaFetch("/api/contacts", {
@@ -364,10 +364,10 @@ export async function writeToMonica(entry) {
           is_deceased_date_known: existingData.is_deceased_date_known ?? false
         };
         if (bday.is_birthdate_known) {
-          putBody.day = bday.day;
-          putBody.month = bday.month;
+          putBody.birthdate_day = bday.day;
+          putBody.birthdate_month = bday.month;
           if (bday.year !== null) {
-            putBody.year = bday.year;
+            putBody.birthdate_year = bday.year;
           }
         }