That's not quite right! The day doesn't change at the Prime Meridian. Here's the correct information:

* The International Date Line (IDL) is where the day officially changes. This line is roughly 180 degrees of longitude away from the Prime Meridian.

* The Prime Meridian (0 degrees longitude) is a line of longitude that defines the starting point for measuring degrees of longitude east and west. It has no bearing on the change of day.

Here's how it works:

* As the Earth rotates eastward, it is necessary to adjust the date to avoid having two different days in the same location.

* The IDL was established as a line where the date changes.

* When you cross the IDL heading east, you gain a day. When you cross it heading west, you lose a day.

So, while the Prime Meridian is a very important line of longitude, it doesn't have any role in determining the change of day.