diff --git a/app-nest/src/bolt/enums/bolt-actions.enum.ts b/app-nest/src/bolt/enums/bolt-actions.enum.ts
index 4fc5dfc..109835f 100644
--- a/app-nest/src/bolt/enums/bolt-actions.enum.ts
+++ b/app-nest/src/bolt/enums/bolt-actions.enum.ts
@@ -1,6 +1,7 @@
 enum BoltActions {
   SYNC_USERS = "sync_users",
   REGISTER_PRESENCE = "register_presence",
+  SELECT_OFFICE_FOR_DATE = "select_office_for_date",
 }
 
 export default BoltActions;
diff --git a/app-nest/src/entities/presence/presence.controller.ts b/app-nest/src/entities/presence/presence.controller.ts
index 6a73d15..9c6eca2 100644
--- a/app-nest/src/entities/presence/presence.controller.ts
+++ b/app-nest/src/entities/presence/presence.controller.ts
@@ -20,4 +20,15 @@ export class PresenceController {
       date,
     });
   }
+
+  @BoltAction(BoltActions.SELECT_OFFICE_FOR_DATE)
+  async selectOfficeForDate({ ack, body, payload }: BoltActionArgs) {
+    await ack();
+    const { value, date } = JSON.parse(payload["selected_option"].value);
+    await this.presenceService.upsert({
+      userId: body.user.id,
+      date: dayjs(date).toDate(),
+      office: value,
+    });
+  }
 }
diff --git a/app-nest/src/entities/presence/presence.entity.ts b/app-nest/src/entities/presence/presence.entity.ts
index 028e15c..26d2dcb 100644
--- a/app-nest/src/entities/presence/presence.entity.ts
+++ b/app-nest/src/entities/presence/presence.entity.ts
@@ -13,8 +13,11 @@ export class Presence {
   @PrimaryColumn({ type: "date" })
   date: Date;
 
-  @Column({ type: "enum", enum: PresenceType })
-  type: PresenceType;
+  @Column({ type: "enum", enum: PresenceType, nullable: true })
+  type: PresenceType | null;
+
+  @Column({ nullable: true })
+  office: string | null;
 }
 
 export type PresenceRepository = Repository<Presence>;
diff --git a/app-nest/src/entities/presence/presence.service.ts b/app-nest/src/entities/presence/presence.service.ts
index 09850e1..6c3ae5c 100644
--- a/app-nest/src/entities/presence/presence.service.ts
+++ b/app-nest/src/entities/presence/presence.service.ts
@@ -10,13 +10,20 @@ export class PresenceService {
     private dataSource: DataSource,
   ) {}
 
-  async upsert(presence: Presence) {
+  async upsert(presence: Partial<Presence>) {
+    // Select only existing cols for the upsert operation to avoid overriding
+    // existing data with defaults/nulls.
+    const primaryKeys = ["userId", "date"];
+    const updatableCols = Object.keys(presence).filter(
+      (key) => !primaryKeys.includes(key),
+    );
+
     return this.dataSource
       .createQueryBuilder()
       .insert()
       .into(Presence)
       .values(presence)
-      .orUpdate(["type"], ["userId", "date"])
+      .orUpdate(updatableCols, primaryKeys)
       .execute();
   }
 }
diff --git a/app-nest/src/gui/tabs/home/day-list-item.blocks.ts b/app-nest/src/gui/tabs/home/day-list-item.blocks.ts
index 6b728f4..1f6d01b 100644
--- a/app-nest/src/gui/tabs/home/day-list-item.blocks.ts
+++ b/app-nest/src/gui/tabs/home/day-list-item.blocks.ts
@@ -34,7 +34,7 @@ const getDayListItemBlocks = ({ date }: DayListItemProps) => [
         },
       },
       {
-        action_id: "text1234",
+        action_id: BoltActions.SELECT_OFFICE_FOR_DATE,
         type: "static_select",
         placeholder: {
           type: "plain_text",
@@ -45,7 +45,7 @@ const getDayListItemBlocks = ({ date }: DayListItemProps) => [
             type: "plain_text",
             text: "Helsinki",
           },
-          value: "hki",
+          value: JSON.stringify({ value: "hki", date: date.toISOString() }),
         },
         options: [
           {
@@ -53,14 +53,14 @@ const getDayListItemBlocks = ({ date }: DayListItemProps) => [
               type: "plain_text",
               text: "Helsinki",
             },
-            value: "hki",
+            value: JSON.stringify({ value: "hki", date: date.toISOString() }),
           },
           {
             text: {
               type: "plain_text",
               text: "Tampere",
             },
-            value: "tre",
+            value: JSON.stringify({ value: "tre", date: date.toISOString() }),
           },
         ],
       },