2023

Update to the page of instructions:
"Days on which particularly interesting phenomena or events occur are highlighted with a purple corner under the date."

2022

Historical date correction—April 10th item should appear on October 4th:
"USSR launched first–ever artificial satellite Sputnik 1 into space 65 years ago."

2017

The April page of the 2017 Observer's Calendar has incorrect values for Moon rise and set times. The correct times are shown in the two PDFs given in the links below. One is for 40 degrees north; the other for 50 degrees north.