Will your little one be born on the 4th of July—or arrive just in time to be your tiny little Valentine? Here's a simple birthdate calculator to give you an idea of when baby will be born based on the time of conception.
Astrolabe. This was used by captains at sea in order to calculate the latitude of the ship, by measuring the angle between the horizon and the sun. This was not a very accurate tool for captain's due to the fact that they did not always take very reliable measurements, especially in inclement weather.