almanac_page almanac_defined almanac_arguments future_event_list calculated_tables early_almanac almanac_etymology astronomy-astrology almanac_and_horoscope yearbook college_yearbook yearbook_aim competition_from_social_media digital_preservation anachronism medieval_navigators Babbages_Difference_Engine US_Naval_Observatory_Table_Printer navigation_annual UKUSA_cooperation periodical_deadlines conference_dates publication_dates venue_timetable