| 1950-68 | 1969-85 | 1986-96 |
| 1918 | |  | | Born August 25 to Jennie (b. Resnick) & Samuel Joseph (Shmuel Yosef) Bernstein, Lawrence, Massachusetts. |
| 1923 | | | | October 23, birth of sister, Shirley Anne. |
| 1928 | | | | First piano lessons, with Frieda Karp. |
| 1929 | | | | June, graduated W. L. Garrison Grammar School, Roxbury, Mass. (1923?-1929) |
| 1930 | | | | Piano lessons with Susan Williams at the New England Conservatory of Music. |
| 1932 | | | | October, piano lessons with Helen G. Coates. |
| 1934 | | | | May 14, first piano recital, Roxbury Memorial High School. |
| | | | Summer, adapted and produced his version of Carmen, Sharon, Mass., also singing the title role! |
| | | | First radio series: "Avol Presents Leonard Bernstein at the Piano," Station WBZ, Boston. |
| | | | Entered Harvard. |
| | | | Piano study with Heinrich Gebhard. |
| 1937 | | | | January, met Dimitri Mitropoulos |
| | | | July, first piano recital, Scituate Yacht Club. |
| | | | November 14, met Aaron Copland. |
| | | | First published writing on music in Modern Music (about David Prall, the aesthetician.) |
| 1938 | | | | June 12, his first public performance as composer-pianist: Music for the Dance Nos. #1 & 2, Music for Two Pianos, with Mildred Spiegel, Brookline. |
| 1939 | | | | April 21, his first appearance as a conductor, leading his own incidental score to The Birds, at Harvard. |
| | | | May 27, directed from the piano, Blitzstein's The Cradle Will Rock, Harvard. |
| | | | June 22, graduated Harvard, cum laude in musica. Music teachers: Edward A. Ballantine, elementary harmony; Edward B. Hill, orchestration; A. Tillman Merritt, harmony and counterpoint; Walter Piston, counterpoint and fugue. |
| 1939 | | | | First television appearance (NBC) as piano accompanist for The Revuers, which included Betty Comden, Adolph Green and Judy Holiday. |
| 1940 | | | | January, first solo recording as a pianist in David Diamond's Prelude & Fugue No. 3 in C# Major, New Music Recordings. |
| | | | March, first recording as an accompanist to The Revuers, The Girl With the Two Left Feet. |
| 1940 | | | | Spent first summer at BMC, Tanglewood, as a conducting student of Serge Koussevitzky. |
| | | | July 11, conducted Boston Pops Orch. at Esplanade open air concert in Wagner's Prelude to Die Meistersinger, his first appearance with a professional orchestra. |
| | | | May 3, received diploma in conducting from Curtis Institute of Music, Philadelphia. Teachers: Fritz Reiner, conducting; Isabella Vengerova, piano; Randall Thompson, orchestration; Richard Stoehr, counterpoint; Renée Longy Miquelle, score reading (1939-41).
| 1942 | | | | April 21, premiere of Sonata for Clarinet and Piano, Boston, David Glazer & Leonard Bernstein (hereinafter referred to as LB). Summer, worked as assistant to Serge Koussevitzky at Tanglewood. |
| 1942-43 | | | | Worked at Harms, Inc., New York publishers, using pseudonym of Lenny Amber. |
| 1943 | | | | April, signed first contract with a music publisher, Harms-Witmark (MPHC). |
| | | | August 24, premiere of I Hate Music, Jennie Tourel & LB, Lenox, Mass. |
| | | | August 25, invited by Artur Rodzinski.to be Assistant Conductor of the Philharmonic-Symphony Society of New York (popularly known as The New York Philharmonic) . |
| | | | Fall, first recording of his own music, Sonata for Clarinet & Piano, David Oppenheim & LB, Hargail recordings. |
| | | | October 18, did workshop readings of American compositions with NYP, Carnegie Hall. |
| | | | November 13, premiere of I Hate Music by Jennie Tourel in Town Hall, NYC. |
| | | | November 14, debut with NYP, substituting for Bruno Walter. |
| | | | December 16, substituted for Howard Barlow with NYP. |
| 1944 | | | | January 28, premiere of Jeremiah, Symphony No. 1, PSO, LB cond., with Jennie Tourel. |
| | | | March 4, conducted first concert outside of US: Les Concerts Symphoniques de Montréal. |
| | | | April 18, conducted premiere of Jerome Robbins' ballet Fancy Free, NYC. Spring, signed first contract with a recording company: RCA-Victor. |
| | | | December 28, premiere of On the Town, NYC. |
| 1945 | | | | January 14, led FP of Fancy Free Suite, PSO. |
| | | | May 11, premiere of Hashkiveinu, Park Avenue Synagogue, NYC. |
| | | | October 8, began three-year directorship of the NYCS. |
| 1946 | | | | April 1, premiere of Blitzstein's Airborne Symphony, NYCS. |
| | | | May 15, made his overseas debut with Czech Philharmonic, Prague. |
| | | | July, first performance, Ravel Piano Concerto in G, Philharmonic Orch. of London as pianist-conductor. |
| | | | July 4, conducted European premiere of Fancy Free with Ballet Theatre at Royal Opera House, London. |
| | | | August 6, conducted American premiere of Britten's Peter Grimes, BMC. |
| | | | October 24, led premiere of Jerome Robbins' ballet Facsimile, Ballet Theatre, NYC. |
| 1947 | | | | April 27, Tel Aviv, gave first of nine concerts with Palestine Philharmonic Orch. |
| 1948 | | | | January 30, led premiere of Shapero's Symphony for Classical Orchestra, BSO. Spring, first European tour conducting different orchestras in Munich, Milan, Budapest, Vienna, Scheveningen, Paris (radio). |
| | | | | May 10, led orchestra of 17 Jewish displaced persons, Holocaust survivors from camps in Landsberg & Feldafing, Germany, in Bizet L'Arlesienne Suite and Gershwin's Rhapsody in Blue. |
| | | | October--November, led concerts of IPO in Israel during the War of Independence. |
| 1949 | | | | April 8, premiere of The Age of Anxiety, Symphony No. 2, BSO, Koussevitzky, cond., LB as piano soloist. |
| | | | December 2, led premiere Messiaen's Turangalîla Symphony, BSO. |
| | | | December 2, film premiere of On The Town, MGM. |
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