Misc: What is a period of play in polo?

Questions

What word is given to the line which forms the boundary between the day and night hemispheres of the moon?

Who, in 1957, was the first-black player to win a singles title at Wimbledon?

Which World Champion heavyweight boxer held the title for the longest?

Which country became the second to issue postage stamps in 1843?

Which author wrote the "Redwall" series of novels?