I believe this is Chromolithography by artist Frances Brundage. The colors are very bright and clean and the children are charming. The calendar is for October, November, December 1900. It measures 10″ x 14 1/2″. It is a page torn from a book as evident on the side and bottom. There is some foxing/staining mostly along the left edge as shown. The three little calendars on the page have their Mondays crossed out. It says Copyright 1899 by John Wanana (which I believe is Wananamaker). Buyer pays for mailing.
Brundage was born Frances Isabelle Lockwood on June 28, 1854 in Newark, New Jersey, to Rembrandt Lockwood and Sarah Ursula Despeaux. Her father was an architect, a wood engraver, and an artist who painted church murals, portraits, and miniatures. Brundage received her art education from her father, and, at the age of seventeen, was forced to earn a living from her art after Lockwood abandoned his family. She sold her first professional work – a sketch illustrating a poem by Louisa May Alcott – to the author.