diff --git a/aero-collections/src/calendar/mod.rs b/aero-collections/src/calendar/mod.rs
index 936f8c3..7e5a8c1 100644
--- a/aero-collections/src/calendar/mod.rs
+++ b/aero-collections/src/calendar/mod.rs
@@ -38,6 +38,8 @@ impl Calendar {
         Ok(Self { id, internal })
     }
 
+    // ---- DAG sync utilities
+
     /// Sync data with backing store
     pub async fn force_sync(&self) -> Result<()> {
         self.internal.write().await.force_sync().await
@@ -49,24 +51,40 @@ impl Calendar {
         self.internal.write().await.opportunistic_sync().await
     }
 
-    pub async fn get(&self, blob_id: UniqueIdent, message_key: &Key) -> Result<Vec<u8>> {
-        self.internal.read().await.get(blob_id, message_key).await
+    // ---- Data API
+
+    /// Access the DAG internal data (you can get the list of files for example)
+    pub async fn dag(&self) -> DavDag {
+        // Cloning is cheap
+        self.internal.read().await.davdag.state().clone()
     }
 
+    /// The diff API is a write API as we might need to push a merge node
+    /// to get a new sync token
     pub async fn diff(&self, sync_token: Token) -> Result<(Token, Vec<SyncChange>)> {
-        self.internal.read().await.diff(sync_token).await
+        self.internal.write().await.diff(sync_token).await
     }
 
+    /// Get a specific event
+    pub async fn get(&self, evt_id: UniqueIdent, message_key: &Key) -> Result<Vec<u8>> {
+        self.internal.read().await.get(evt_id, message_key).await
+    }
+
+    /// Put a specific event
     pub async fn put<'a>(&self, entry: IndexEntry, evt: &'a [u8]) -> Result<Token> {
         self.internal.write().await.put(entry, evt).await
     }
 
+    /// Delete a specific event
     pub async fn delete(&self, blob_id: UniqueIdent) -> Result<Token> {
         self.internal.write().await.delete(blob_id).await
     }
 }
 
+use base64::Engine;
+const MESSAGE_KEY: &str = "message-key";
 struct CalendarInternal {
+    #[allow(dead_code)]
     id: UniqueIdent,
     cal_path: String,
     encryption_key: Key,
@@ -90,16 +108,37 @@ impl CalendarInternal {
     }
 
     async fn put<'a>(&mut self, entry: IndexEntry, evt: &'a [u8]) -> Result<Token> {
-        //@TODO write event to S3
-        //@TODO add entry into Bayou
-        todo!();
+        let message_key = gen_key();
+        
+        let encrypted_msg_key = cryptoblob::seal(&message_key.as_ref(), &self.encryption_key)?;
+        let key_header = base64::engine::general_purpose::STANDARD.encode(&encrypted_msg_key);
+
+        // Write event to S3
+        let message_blob = cryptoblob::seal(evt, &message_key)?;
+        let blob_val = BlobVal::new(
+            BlobRef(format!("{}/{}", self.cal_path, entry.0)),
+            message_blob,
+        )
+        .with_meta(MESSAGE_KEY.to_string(), key_header);
+
+        self.storage
+            .blob_insert(blob_val)
+            .await?;
+
+        // Add entry to Bayou
+        let davstate = self.davdag.state();
+        let put_op = davstate.op_put(entry);
+        let token = put_op.token();
+        self.davdag.push(put_op).await?;
+
+        Ok(token)
     }
 
     async fn delete(&mut self, blob_id: BlobId) -> Result<Token> {
         todo!();
     }
 
-    async fn diff(&self, sync_token: Token) -> Result<(Token, Vec<SyncChange>)> {
+    async fn diff(&mut self, sync_token: Token) -> Result<(Token, Vec<SyncChange>)> {
         todo!();
     }
 }