How to include the current timestamp in an alert message?

I’ve a request to include the time when an alert was raised in the message body of the alert.

I’ve checked out Create Alerts and Alert notification templates and it looks like it might be possible, but I can’t find any reference to any list of supported variables.

For reference, we’re using Grafana v7.4.0 (c2203b9859) and creating an alarm off a cloudwatch metric query:

REMOVE_EMPTY(SEARCH('{"AWS/ApiGateway","ApiName","Method","Resource","Stage"} MetricName="5XXError"', 'Sum', 60))

What I’m trying to do is include something like this, in the email being sent out when this alert is triggered (although the actual date format doesn’t matter at all):

Alert raised at 2021-08-26T12:03