diff --git a/src/ContactEdit.tsx b/src/ContactEdit.tsx
index 11a79ed..5f04f03 100644
--- a/src/ContactEdit.tsx
+++ b/src/ContactEdit.tsx
@@ -259,6 +259,7 @@ class ContactEdit extends React.Component {
     comp.updatePropertyWithValue('version', '4.0');
     comp.updatePropertyWithValue('uid', this.state.uid);
     comp.updatePropertyWithValue('fn', this.state.fn);
+    comp.updatePropertyWithValue('rev', ICAL.Time.now());
 
     function setProperties(name: string, source: ValueType[]) {
       comp.removeAllProperties(name);
diff --git a/src/EventEdit.tsx b/src/EventEdit.tsx
index 1921923..4bd8ec9 100644
--- a/src/EventEdit.tsx
+++ b/src/EventEdit.tsx
@@ -135,6 +135,8 @@ class EventEdit extends React.Component {
     event.location = this.state.location;
     event.description = this.state.description;
 
+    event.component.updatePropertyWithValue('last-modified', ICAL.Time.now());
+
     this.props.onSave(event, this.state.journalUid, this.props.event);
   }
 
diff --git a/src/ical.js.d.ts b/src/ical.js.d.ts
index 1d30e97..4695542 100644
--- a/src/ical.js.d.ts
+++ b/src/ical.js.d.ts
@@ -60,6 +60,8 @@ declare module 'ical.js' {
 
     static fromString(str: string): Time;
 
+    static now(): Time;
+
     constructor(data?: {
       year?: number,
       month?: number,