There are 2 direct scriptures which directly teach that one prophetic day represents one actual year.
1) Numbers 14:34 “After the number of the days in which ye searched the land, even forty days, each day for a year, shall ye bear your iniquities, even forty years, and ye shall know my breach of promise.”
2) 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.”
But what is really exciting is when we apply this principle to prophetic messages such as Daniel 9:24. This verses speaks of a period of 70 weeks. (70 weeks x 7 days in a week = 490 days => 490 years)
The first 69 weeks (69 x 7 = 483 years) are explained in Daniel 9:25 “Know therefore and understand, that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks:”
We see that 7 weeks (7 x 7 days in a week) + 3 score (3 x 20 x 7 days in a week) and 2 weeks (2 x 7days in a week) = (49)+(420)+(14)=483 days or 483 years.
The beginning of the building of Jerusalem has an established date of 454BC. Adding 483 years to 454BC brings us to 29AD which is exactly when “Jesus our Messiah” began his ministry.
Continuing further, the 70th week (7 years) is spoken of in Daniel 9: 27. “And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease”. In the final week in the midst (midst meaning middle, or 3 ½ years into the 70th week) God shall “cause the sacrifice…to cease.” Jesus’ sacrifice was completed and he was crucified in 33AD. Exactly as Daniel had prophesied in Daniel 9!
This amazing application of a day for a year concept proves exactly when Christ was to begin his ministry and when he was to die.