When was the debut album released?
The sources are more or less evenly split between 11th April and 14th April 1980. An announcement in the New Musical Express from 29.03.1980 says 11th (
here - this is also cited by Wiki), the Commentary also says 11th. The official website and
@Luisma's book say 14th. 11th was a Friday, 14th was a Monday. All other Maiden records from 1980 were released on Fridays, with the only exception being Women in Uniform, on a Monday. However, the NME piece is only an advance announcement, and the release date might have changed since. I don't know where the IMC has its date from. With the official Maiden site, you'd think they would get that right, but it's full of errors.
I'm thinking Loopy's book may have reliable information, but it's not accessible to me right now.