set {timestamp} af cookie with Cookiemoster plugin

I want to set a cookie with the timestamp of today's date, but when i use {{ cookie_monster:put key="last_visit" value="{timestamp}" }} The value in my cookie is 'deleted'

When place {now} as value {{ cookie_monster:put key="last_visit" value="{now}" }}

the output is a formatted time stamp 'May+14th%2C+2019'

I can't compare the now value with a timestamp

Does anyone know how i can set the value as an timestamp

Thanks