How do we know what 1 day is in prophecy?
When we go do Daniel 9 Gabriel says that from Jerusalem rebuilt to Messiah or Jesus anointed of baptised is 69 Weeks .
DA 9 24 'Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy.'
If we take Jerusalem rebuilt in 457 bc and add 69 weeks we arrive to just a few years later. The question is was Jesus baptised around 450 bc. No This does not make sense .
Then the only sensible conclusion is that a day cannot be a year . As it cannot fit bible prophecy . But when we take one day for a year principle which fits all prophecies . We find out that taking Jerusalem rebuilt in 457 bc we add 69 weeks BY 7 which is 483 years We arrive to year 27 when Jesus was baptised .
Also when Gabriel says keep this book for it is for the end of time. Then one day cannot be one literal day .
DA 12 4 But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased....6 And one said to the man clothed in linen, which was upon the waters of the river, How long shall it be to the end of these wonders?
7 And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished.
...8 And I heard, but I understood not: then said I, O my Lord, what shall be the end of these things?
9 And he said, Go thy way, Daniel: for the words are closed up and sealed till the time of the end.'
Here we see that the prophecies of the book of Daniel refer to the end of time. So the days cannot be days but years . As the 1260 days refer to the reign of the antichrist . Did the antichrist reign 1260 days ? No The 2300 days when Jesus would enter the most holy place does it mean that 2300 days after Jerusalem was rebuild in 457 Jesus entered the most holy place,? No as Jesus was not yet born ?
So we see that the day year principle given by God to William Miller is valid and is the only correct day interpretation in bible prophecy .
NU 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.'
EZ 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. '