Significant Dates in Professional Hockey History
| Date | Description |
| 1917-11-26 | NHL is formed with charter franchises Montreal Canadiens, Montreal Wanderers, Ottawa Senators, Quebec Bulldogs (elected not to operate a team until 19-20 season), and Toronto Arenas |
| 1917-12 | Montreal Wanderers withdrew from NHL |
| middle of 1918-19 season | Toronto Arenas withdrew from NHL |
| 1919-10-01 | Toronto Arenas reorganized under new ownership and re-joined NHL as Toronto St. Patricks |
| prior to 1920-21 season | Quebec Bulldogs moved to Hamilton and renamed Tigers |
| 1924-10-11 | NHL expansion franchises granted to Boston (Bruins) and Montreal (Maroons) |
| 1925-09-22 | NHL dropped Hamilton Tigers franchise and their players were assigned to a new franchise, the New York Americans |
| prior to 1925-26 season | Pittsburgh Pirates joined NHL |
| prior to 1926-27 season | Chicago Blackhawks and Detroit Cougars joined NHL |
| 1926-05-15 | NHL franchises granted to Detroit (Cougars) and New York (Rangers) |
| during 1926-27 season | St. Patricks renamed Maple Leafs |
| 1930-10-18 | Pittsburgh Pirates moved to Philadelphia and renamed Quakers |
| prior to 1930-31 season | Detroit Cougars renamed Falcons |
| prior to 1931-32 season | Ottawa Senators and Philadelphia Quakers folded |
| prior to 1932-33 season | Ottawa Senators re-joined NHL |
| 1932-10-05 | Detroit Falcons renamed Red Wings |
| 1934-05-13 | Ottawa Senators moved to St. Louis and renamed Eagles |
| 1935-10-15 | St. Louis Eagles franchise purchased by NHL and suspended operations |
| 1935-10-15 | NHL dispersal draft (St. Louis Eagles) |
| 1963-06-05 | 1963 NHL amateur draft |
| 1964-06-11 | 1964 NHL amateur draft |
| 1965-04-27 | 1965 NHL amateur draft |
| 1966-04-25 | 1966 NHL amateur draft |
| 1967-06-05 | NHL expansion franchises awarded to California (Seals), Los Angeles (Kings), Minnesota (North Stars), Philadelphia (Flyers), Pittsburgh (Penguins), St. Louis (Blues) |
| 1967-06-06 | NHL expansion draft (California Seals, Los Angeles Kings, Minnesota North Stars, Philadelphia Flyers, Pittsburgh Penguins, St. Louis Blues) |
| 1967-06-07 | 1967 NHL amateur draft |
| 1967-11-06 | California Seals renamed Oakland Seals (date per answers.com, date 1967-12-08 per www.sealshockey.com) |
| 1968-06-13 | 1968 NHL amateur draft |
| 1969-06-12 | 1969 NHL amateur draft |
| 1970-05-22 | NHL expansion franchises awarded to Buffalo (Sabres) and Vancouver (Canucks) |
| 1970-06-11 | 1970 NHL amateur draft |
| 1970-07-01 | Oakland Seals renamed California Golden Seals (date approximate) |
| 1971-06-10 | 1971 NHL amateur draft |
| 1971-08-01 | WHA charter franchise awarded to Minnesota (Fighting Saints) |
| 1971-11-09 | NHL expansion franchise awarded to Atlanta (Flames) and New York (Islanders) to begin play in 1972-73 season |
| 1971-11-01 | Winnepeg Jets admitted to WHA |
| 1972-02-12 — 1972-02-13 | WHA General Player Draft |
| 1972-06-06 | NHL expansion draft (Atlanta Flames and New York Islanders) |
| 1972-06-08 | NHL expansion franchises awarded to Kansas City (Scouts) and Washington (Capitals) to begin play in 1974-75 season |
| 1972-06-08 | 1972 NHL amateur draft |
| 1973-05 | New York Raiders (WHA) renamed Golden Blades |
| 1973-05-15 | 1973 NHL amateur draft |
| 1973-09-14 | Indiapolis Racers (WHA) awarded WHA franchise to begin play in 1974-75 |
| 1974-04-30 | New Jersey Knights (WHA) moved to San Diego and renamed Mariners |
| 1974-05-28 | 1974 NHL amateur draft |
| 1974-06-12 | expansion draft for Kansas City Scouts and Washington Capitals |
| 1975-01-18 | Michigan Stags (WHA) folded |
| 1975-01-25 | remains of Michigan Stags (WHA) moved to Baltimore and named Blades (WHA) |
| 1975-05-19 | Denver Spurs (WHA) granted an expansion franchise to begin play in 1975-76 season |
| 1975-05 | Chicago Cougars (WHA) folded |
| 1975-06-18 | Baltimore Blades (WHA) folded |
| 1975-06-19 | WHA dispersal draft of Baltimore Blades (WHA) and Chicago Cougars (WHA) players |
| 1976-02-27 | Minnesota Fighting Saints (WHA) folded |
| 1976-07-15 | Kansas City Scouts moved to Colorado and renamed Rockies |
| 1976-07-15 | California Golden Seals moved to Cleveland and renamed Barons |
| 1977-01-17 | Minnesota Fighting Saints (WHA) folded |
| 1977-04-06 | Phoenix Roadrunners (WHA) folded |
| 1977-06-14 | 1977 NHL amateur draft |
| 1977-05-31 | Calgary Cowboys (WHA) folded |
| 1978-06-15 | Cleveland Barons - Minnesota North Stars merger/dispersal draft |
| 1979-06-22 | Four former WHA teams (Edmonton Oilers, Hartford Whalers, Quebec Nordiques and Winnipeg Jets) admitted to NHL |
| 1979-08-09 | 1979 NHL entry draft |
| 1980-06-11 | 1980 NHL entry draft |
| 1980-06-24 | Atlanta Flames moved to Calgary |
| 1981-06-10 | 1981 NHL entry draft |
| 1982-05-27 | Colorado Rockies moved to New Jersey and renamed Devils |
| 1982-06-09 | 1982 NHL entry draft |
| 1983-06-08 | 1983 NHL entry draft |
| 1984-06-09 | 1984 NHL entry draft |
| 1985-06-15 | 1985 NHL entry draft |
| 1986-06-21 | 1986 NHL entry draft |
| 1987-06-13 | 1987 NHL entry draft |
| 1988-06-11 | 1988 NHL entry draft |
| 1989-06-17 | 1989 NHL entry draft |
| 1990-05-09 | NHL expansion franchise awarded to San Jose (Sharks) |
| 1990-06-16 | 1990 NHL entry draft |
| 1990-12-07 | NHL expansion franchises awarded to Ottawa (Senators) and Tampa Bay (Lightning) to begin play in 1992-93 season |
| 1991-05-30 | NHL dispersal draft (Sharks drafted players from North Stars per agreement) and expansion draft (Sharks and North Stars drafted players from all other NHL teams) |
| 1991-06-22 | 1991 NHL entry draft |
| 1992-06-20 | 1992 NHL entry draft |
| 1992-12-10 | NHL expansion franchise awareded to Anaheim (Mighty Ducks) and Florida (Panthers) to begin play in 1993-94 season |
| 1993-06-09 | Minnesota North Stars franchise moved to Dallas and renamed Stars |
| 1993-06-24 | NHL expansion draft (Mighty Ducks and Panthers) |
| 1993-06-26 | 1993 NHL entry draft |
| 1994-06-28 | 1994 NHL entry draft |
| 1996-01-19 | Winnipeg Jets relocation to Phoenix approved by NHL |
| 1995-06-21 | Quebec Nordiques moved to Colorado and renamed Avalanche |
| 1996-06-22 | 1996 NHL entry draft |
| 1996-07-01 | Winnipeg/Phoenix Jets renamed Coyotes |
| 1997-06-21 | 1997 NHL entry draft |
| 1997-06-25 | Hartford Whalers franchise moved to Carolina and renamed Hurricanes |
| 1997-06-25 | NHL expansion franchises granted to Atlanta (Thrashers), Columbus (Blue Jackets), Minnesota (Wild), and Nashville (Predators) |
| 1998-06-26 | 1998 NHL expansion draft (Nashville Predators) |
| 1998-06-27 | 1998 NHL entry draft |
| 1999-06-25 | NHL expansion draft (Atlanta Thrashers) |
| 1999-06-26 | 1999 NHL entry draft |
| 2000-06-23 | NHL expansion draft (Columbus Blue Jackets, Minnesota Wild) |
| 2000-06-24 — 2000-06-25 | 2000 NHL entry draft |
| 2001-06-23 — 2001-06-24 | 2001 NHL entry draft |
| 2002-06-22 — 2002-06-23 | 2002 NHL entry draft |
| 2003-06-21 — 2003-06-22 | 2003 NHL entry draft |
| 2004-06-26 — 2004-06-27 | 2004 NHL entry draft |
| 2005-07-30 | 2005 NHL entry draft |
| 2006-06-22 | Mighty Ducks renamed Ducks |
| 2006-06-24 | 2006 NHL entry draft |
| 2007-06-22 — 2007-06-23 | 2007 NHL entry draft |
| 2008-06-20 — 2008-06-21 | 2008 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2009-06-27 — 2009-06-28 | 2009 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2010-06-25 — 2010-06-26 | 2010 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2011-05-31 | Atlanta Thrashers moved to Winnipeg |
| 2011-06-24 — 2011-06-25 | 2011 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2012-06-22 — 2012-06-23 | 2012 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2013-06-30 | 2013 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2014-06-27 — 2014-06-28 | 2014 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2015-06-26 — 2015-06-27 | 2015 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2016-06-22 | Las Vegas expansion franchise approved to begin play in 2017-18 season |
| 2016-06-24 — 2016-06-25 | 2016 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2017-06-18 — 2017-06-20 | NHL expansion draft (Vegas Golden Knights) |
| 2017-06-23 — 2017-06-24 | 2017 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2018-06-22 — 2018-06-23 | 2018 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2019-06-22 — 2019-06-23 | 2019 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |
| 2020-10-06 — 2020-10-07 | 2020 NHL entry draft (round 1 on day 1, rounds 2-7 on day 2) |