[Home](./index.md) > [@snowplow/browser-tracker](./browser-tracker.md) > [ClientSession](./browser-tracker.clientsession.md) > [firstEventTimestamp](./browser-tracker.clientsession.firsteventtimestamp.md) ## ClientSession.firstEventTimestamp property Date-time timestamp of when the first event in the session was tracked Signature: ```typescript firstEventTimestamp: string | null; ```