I think you have it backwards. Days are getting longer. So assuming tidal lock with Sun in the future which means 1 year = 1 day (1 revolution per year). So how

I think you have it backwards. Days are getting longer. So assuming tidal lock with Sun in the future which means 1 year = 1 day (1 revolution per year). So how long until 1 day becomes 365 days long. Assuming the 30min per 70M years is linear, this would take 1.2 Trillion years. Somebody double check this please. ;) Also, the Sun will only last for another 4B years.