Ezekiel 4:6
And when thou hast accomplished them, lie again on thy right side, and thou shalt bear the iniquity of the house of Judah forty days: I have appointed thee each day for a year. And when thou hast accomplished them, lie again on thy right side, and thou shalt bear the iniquity of the house of Judah forty days: I have appointed thee each day for a year.
In symbolic prophecy a day represents a year, each prophetic day standing for one literal year. This day-for-a-year rule is the appointed measure for interpreting prophetic periods as years. Prophetic time periods are therefore to be read as years rather than literal days.
The forty days appointed in the verse itself therefore signify forty years. This principle supports studying the time periods in Daniel and Revelation, which are meant to be understood and were expected to reach their end around that era. Applied to Daniel's seventy weeks, the 490 prophetic days are 490 years.
Applied to the 2300 days in Daniel 8, the period is 2300 years. The 2300 years end in 1844, and expecting the end in the spring rather than the autumn caused disappointment but did not change the year or the event connected with the period's close.