Yes, and that concept has been helpful to Bible students in their efforts to understand time prophecy. Ellen White, commenting on William Miller's method of study, wrote:

Following his rule of making Scripture its own interpreter, Miller learned that a day in symbolic prophecy represents a year (Numbers 14:34; Ezekiel 4:6); he saw that the period of 2300 prophetic days, or literal years, would extend far beyond the close of the Jewish dispensation, hence it could not refer to the sanctuary of that dispensation. (The Great Controversy, p. 324)

The concept that a day in prophecy represents a year is true in many cases. In fact, it is true for all of the historical time prophecies. However, have you ever wondered why the millennium is 1,000 literal years, rather than 360,000, as it would be if every day of the prophecy were interpreted as a year of literal time? Yet, there is nothing in Numbers 14:34 or Ezekiel 4:6 to tell us why a day should be interpreted as a year sometimes but not always.

We need a more thorough understanding of this important principle.

A good place to start is the 70 weeks prophecy of Daniel 9. When Gabriel came to give Daniel a further explanation of the vision containing the 2,300 evenings-mornings prophecy, he told him,

"Seventy weeks are decreed for your people and your holy city to finish transgression, to put an end to sin, to atone for wickedness, to bring in everlasting righteousness, to seal up vision and prophecy, and to anoint the most holy.

"Know and understand this: From the issuing of the decree to restore and rebuild Jerusalem until the Anointed One, the ruler, comes, there will be seven weeks and 62 weeks" (Daniel 9:24-25).

A week in the Bible is a period of either seven days or seven years (Leviticus 25:1-7). The decree to restore and rebuild Jerusalem was issued in the spring (first month) of Artexerxes' seventh year (457 BC). Ezra 7 gives the account. Jesus became the Anointed One at his baptism in AD 26/27, the 15th year of Tiberius Caesar (Luke 3)--483, or 69 x 7, years later. Therefore, the 70 weeks are not 70 weeks of days but 70 weeks of years.

Gabriel told Daniel that he had come to give him understanding of the vision (Daniel 9:23)--the vision recorded in Daniel 8. One point that needed further explanation was the 2,300 evenings-mornings. No beginning point had been given. Now, Gabriel tells Daniel that the 70 weeks are "cut off" (the meaning of the word "decreed") from the larger time period of the 2,300 evenings-mornings. Therefore, since the basic unit of the 70 weeks is the year, rather than the day, the 2,300 evenings-mornings are to be counted as years instead of days also.

This brings the application of the day-year principle all the way to 1844. However, it does not demand that any time prophecies after 1844 be so reckoned. In fact, as we have already observed, the millennium is interpreted as a literal 1,000 years. Therefore, it would appear that the application of the day-year principle comes to an end sometime between 1844 and Jesus' second coming.