historical astronomy anniversaries month

Would anyone like to contribute an interesting historical date around the theme of Astronomy?
If I start a thread for a month, whoever has an interesting date for that month can post it.
After the date, just put a sentence or two as an explanation.
Can we find something for every day of the selected month?

Date: Day Month Year

Relevance: Just a couple of sentences as to why it is important this month.

Ok, now look for the thread for the month.