Roughly the year 13,789,000,000 - dating from the beginning of the universe. All dates are calculated relative to something and that something can be pretty arbitrary. The problem is that the farther back we go in history, the less certain dates become except when we can anchor them to things we can calculate precisely from the present, like some astronomical phenomena.

Could you clarify your question a bit more? Days don't have some innate numbering system attached to them, so it's impossible to say what today's "actual" date is without referencing one subjective calendar system or another.