@Johnjohnjohn,
The Hebrew word that is translated here in Daniel is "yom" which indicates a significant period of time, not always
Perhaps the 1290 "yoms" of Daniel do not relate to days... some examples perhaps
In Genesis 1:5 Yom is referred to as a period of light, (12ish hours?)
It appears all six Yoms were referred to as a single yom in Genesis 2:4. (a week?)
In Genesis 4:3. Cains crops grew in a single Yom (a few months?)
In Genesis 43:9 Moses declares that he shall bare the blame for Yom (eternity?)