Why is Easter when Easter is?

Here's some help from anonymous source in an e-mail my mom sent to me about the date of Easter:

Easter this year is Sunday March 23 2008. Easter is always the 1st Sunday after the 1st full moon after the Spring Equinox (which is March 20). This dating of Easter is based on the lunar calendar that Hebrew people used to identify passover. This is why it moves around on our Roman calendar. Based on the above Easter can only be one day earlier (March 22) than it will be this year, and falling on March 22 is pretty rare. This year Easter is the earliest any of us will ever see for the rest of our lives! and only the most elderly of our population have ever seen it this early (95 years old or above) and none of us have ever of will ever see it a day earlier! Here are the facts: The next time Easter will be this early (March 23) will be in the year 2228 (220 years from now). The last time it was this early was in 1913. The next time it will be a day earlier (March 22) will be in the year 2285 (277 years from now). The last time it was on March 22 was in 1818.