Yes, in ancient times the year was held to be at 360 days. The fact that the prophets understood a year as 360 days is well attested, and can be seen in the prophecies of Daniel and Revelation which are based on the 360 day Jewish year.You didn't mention which calendar was used for the calculations. The Jewish calendar was different to our Gregorian calendar. This may make a difference. If the Jewish calendar was used, the calculations would be more accurate and consistent with the Biblical record. However you may know this already, so I was just sayin'. :)
The fact that a day can signify a year is of crucial importance in the study of Bible Prophecy. This view was recognized by the Jews as seen in Daniel 9:24-27, and as seen in Jesus' use of the day-year principle in Luke 13 verses 31-33, and in the early church. The Reformers and many others, Martin Luther, John Calvin, Ulrich Zwingli, John Wycliffe, John Knox, William Tyndale, Phillip Melanchthon, Sir Isaac Newton, Jan Huss, John Foxe, John Wesley, Jonathan Edwards, George Whitefield, Charles Finney, C. H. Spurgeon, Matthew Henry, Adam Clarke, Albert Barnes, E. B. Elliot, H. Grattan Guinness, and Bishop Thomas Newton understood this to name just a few.
Lets start with the prophecy in Daniel 9 in which seventy literal weeks would not be enough time to accomplish all the things mentioned as having to transpire within the scope of Daniel's "seventy-weeks" vision. For this reason, most Biblical scholars view the seventy weeks of Daniel as symbolic years:
Daniel 9:24-27 King James Version (KJV)
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.
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: the street shall be built again, and the wall, even in troublous times.
26 And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof shall be with a flood, and unto the end of the war desolations are determined.
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, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate.
Now if you look at the prophecy of seventy weeks in Daniel chapter 9, the 490 years is an uninterrupted period starting from "the time the word goes out to rebuild and restore Jerusalem," of Daniel 9:25 and ending 3½ years after Jesus' death. The starting point identified with a decree by Artaxerxes I in 458/7 BC to provide money to rebuild Jeruslaem and its temple. The appearance of "Messiah the Prince" at the end of the 69 weeks (483 years) is aligned with Jesus' baptism in 27 AD. The 'cutting off' of the "anointed one" is applied to the Jesus' execution 3½ years after the end of the 483 years, bringing "atonement for iniquity" and "everlasting righteousness". Jesus' death is said to 'confirm' the "covenant" between God and mankind by in 31 AD "in the midst of" the last seven years. The end of the 70th week is associated with 34 AD when the gospel was redirected from only the Jews to all peoples.
Christian historicism, which is what unveils these verses from scripture, interprets prophecy as an overview of the history of the Christian church, asserting connections between historical events and statements in the Bible, and distinguishing between prophecies considered already fulfilled and those still to come. The Jews of biblical times, had taught this view in the many prophecies to be fulfilled, which were pointing to the Messiah such as those by the prophets Isaiah and Ezekiel. The early church and the precursors to the Reformation used it, Jerome in his 'Commentary on Daniel' went into the kingdoms that Daniel predicted. Many Protestant Reformers were interested in historicism and the day-year principle, and used it assigning prophecies in the Bible to past, present and future events. It was prevalent in Wycliffe's writings and taught by Martin Luther, John Calvin, John Wesley, and Sir Isaac Newton and many others as we can see.