Poetic or archaic reading of 朝. In modern Japanese, 朝 is read あさ for 'morning', while あした normally means 'tomorrow'. This reading appears mainly in classical poetry or literary contexts.
See also: 朝 (あさ)
A landscape sung of as 'the fields of morning' in an old poem.
The reading あした for 朝 is an older form; in classical Japanese it could mean 'morning' or 'next morning', which later shifted to 'tomorrow' in modern usage. The kanji 朝 itself is conventionally associated with 'morning'.