Historical clue formulations

• Race held annually in early March — 2023-05-21
• Annual competition that starts on the first Saturday in March — 2023-02-10
• The "Last Great Race on Earth" — 2020-05-17
• Dog days of winter? — 2020-03-29
• Northern race — 2020-02-02
• 1,049-mile race — 2018-06-06
• Annual event covering about 1,000 miles — 2017-06-24
• Dashing through the snow? — 2012-07-28
• Race that takes a northern trail in even years and a southern trail in odd years — 2010-06-06
• 1,100-mile run — 2001-05-02