Because people get it wrong! God does not though and He has His dates set in His Word! They are His Feasts His mo'adim(מועדים) which means His appointed times or appointments in time .
Read Leviticus 23 and see that they are HIS Feasts and not Israel's not people's Feasts no they are HIS.(Lev 23:2 Speak unto the children of Israel, and say unto them, Concerning the feasts of the LORD, which ye shall proclaim to be holy convocations, even these are MY feasts. )
Yeshua has set these 7 Feasts of His in the order He fulfils them. The first time He came He fulfilled 4 of those first four Feasts of His in the order He set them out. The whole Universe is His Divinely appointed time piece, a clock so accurate it measures to the smallest time unit to fulfil His Great plan from creation to redemption of mankind showing how Great He is and we can still not comprehend how Great He is. We are too small to understand His Greatness.
Having therefore fulfilled the first four of His Feasts we have an accurate record in His Word as to when and where these Feasts have occurred having been given the signs in the Heavens in His Word and what to look for. (Psalm 19:1 To the chief Musician, A Psalm of David. The heavens declare the glory of God; and the firmament sheweth his handywork. ) He gave us the stars, the Sun and the Moon for signs and seasons! (Genesis 1:14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: ) The word where it says seasons in the English in Hebrew says mo'adim meaning His appointed times(His set dates) indicated to us by the stars and their positions in the Heavens and as the hands of a clock He has given us the Sun and Moon and the wandering stars(the planets).
Did you know God has even told us in His Word how many planets there are in our solar system? I bet you didn't but He showed them to Joseph in a dream and within that dream He gave us a sign! (Genesis 37:9 And he dreamed yet another dream, and told it his brethren, and said, Behold, I have dreamed a dream more; and, behold, the sun and the moon and the eleven stars made obeisance to me. 37:10 And he told it to his father, and to his brethren: and his father rebuked him, and said unto him, What is this dream that thou hast dreamed? Shall I and thy mother and thy brethren indeed come to bow down ourselves to thee to the earth? 37:11 And his brethren envied him; but his father observed the saying. ) Notice here Joseph says the eleven stars, these are the wandering stars which we now know as our solar system's planets notice too the twelfth one is missing which we now know as the asteroid belt! In ancient times before the flood they were aware of twelve planets that orbited the Sun however the one between Jupiter and Mars which was known by the ancients as Phaeton was smashed in the very calamity that ended up causing the great flood of Noah.
My point is these planets or wandering stars have always indicated to those who study them and the Word of God His appointed times are shown in them with an amazing accuracy no one can deny once seen. From the ancient study of the stars we have the many Magi that came to bring 3 gifts to Yeshua after seeing the sign of His birth and following His Star(which we now know as Jupiter because of idolatrous Magi having corrupted the Godly Zodiac) (Matthew 2:2 Saying, Where is He that is born King of the Jews? for we have seen His star in the east, and are come to worship Him. ) The knowledge the Magi(Magos in Greek meaning wise ones) are they who were trained by Daniel the prophet who was put in charge of all the wise men of Babylon most of which were Jews. Daniel had passed on the knowledge to them of reading the stars in secret as God had told him to hide the matter! (Daniel 9:21 Yea, whiles I was speaking in prayer, even the man Gabriel, whom I had seen in the vision at the beginning, being caused to fly swiftly, touched me about the time of the evening oblation. 9:22 And he informed me, and talked with me, and said, O Daniel, I am now come forth to give thee skill and understanding. 9:23 At the beginning of thy supplications the commandment came forth, and I am come to shew thee; for thou art greatly beloved: therefore understand the matter, and consider the vision. ) Once Daniel had been shown the visions and been taught how to tell by the stars and when the Lord's Feasts fulfilments approached he was told to seal up the vision until the time of the end (Dan 12:9 And he said, Go thy way, Daniel: for the words are closed up and sealed till the time of the end. )which happens to be the time in which we live now! Therefore this knowledge has become unsealed by God's Holy Spirit in these last days and has been shown to His servants cleverly hidden in His Word are all we need to know the times of His Feast fulfilments!
We are in the time where God has increased our knowledge of His plan and the Feasts and the fulfilments thereof. (Daniel 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.)
We have been given the greatest sign in the book of Revelation in chapter 12 verse one! That sign happens to be in the Heavens on the 23rd of September 2017 and it is from this date we can with modern stellar software(increased knowledge) tell the time of all other signs given in God's Word.
We can know the date of His birth which was the 11th of March of 4 BC according to our Gregorian calendar count but on that day it happened to be the first day of Nisan on God's calendar the 1st day of the new year. Exactly 14 days later it was Pesach another of His appointed times which He fulfilled on the 3rd of April 33 AD which was exactly Pesach the day He died for our sins! The sign in the sky that very day was to indicate the end of the 69th week of Daniel. "Jupiter"(the King planet) was in the middle of "Gemini"(the two criminals on the cross either side of Him)
Here comes the cracker, in 2014 on the 13th of April that exact same sign was in the sky on the exact same day in God's calendar the 14th of Nisan which is Pesach and not only that but it was to be the first of 4 blood moons over the next 2 years indicating to us the 70th week of Daniel had commenced and God's prophetic clock has once again been set in motion.
It is exactly 1260 days to the 23rd of September this year indicating that we are exactly halfway the 70th week of Daniel on that day. I can hear those minds ticking over and saying what about the antichrist? He is of no interest to those of us with our eyes on Yeshua! But he sets up the abomination that causes desolation I can hear you say! Wrong, the very verse in Daniel which speaks of this time has since a long time been translated wrong and has been allowed to be so because Daniel was told to seal the Word. Let's look at the verse in question!
(Dan 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, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate. ) in Hebrew it reads like this, ( והגביר ברית לרבים שׁבוע אחד וחצי השׁבוע ישׁבית זבח ומנחה ועל כנף שׁקוצים משׁמם ועד־כלה ונחרצה תתך על־שׁמם׃) Knowing Hebrew when I first read it I noticed no breaks were given in the verse such as is in the KJV text above, in Hebrew the same sign is given to break a verse in parts, this sign :
Notice in the KJV text that sign is put in after the one week! In the Hebrew however it does not do this and this is why, the verse literally translated says this and not what you read above in the KJV text, here is what it says, (Daniel 9:27 And he made a covenant with the leaders for one and a half week, on the seventh day he shall put an end to the sacrifice and the offering and set on the cover the abomination that causes desolation) Anyone who knows Hebrew will be able to read the same without question the time given in this verse says "one week and a half" every time! Shavuah Echad veChatzi. And as anyone knows God's perfect number is seven and not ten and a half yet have a look as to who is making the covenant with the many!
The son of perdition is the one making this covenant which he will break not in the middle but after a week(7 years) thus after the 70th week of Daniel. This is the period of God's Wrath those final 3 and a half years of the son of perdition's evil covenant in which God will keep Israel safe in the wilderness.(Revelation 12:13 And when the dragon saw that he was cast unto the earth, he persecuted the woman which brought forth the man child. 12:14 And to the woman were given two wings of a great eagle, that she might fly into the wilderness, into her place, where she is nourished for a time, and times, and half a time, from the face of the serpent. 12:15 And the serpent cast out of his mouth water as a flood after the woman, that he might cause her to be carried away of the flood. 12:16 And the earth helped the woman, and the earth opened her mouth, and swallowed up the flood which the dragon cast out of his mouth. )
Having then the times and the dates of the Feasts we also have the appointed times dates Yeshua has given us in His Word.
The first fulfilment of His latter Feasts is Yom Teruah(the Feast of Trumpets) during which He will remove His 5 wise virgins half of His Bride, those who are prepared for Him and have made ready for the marriage! We know this will occur on the 22nd or 23rd of September as these are the possible dates for Yom Teruah, on the 22nd there is the sign of the sickle in the sky and the day after it is the Revelation 12:1 sign. The 5 foolish virgins will realise they have another 1260 days to go from there once they wisen up and follow their Lord and return to their first love with all their hearts! They will also know that they will be taken through the time of purification with the knowledge they have to go through the hour of temptation which is the day the son of perdition will give them a choice to live and be lost eternally by taking his evil mark or where they will choose life eternal instead and take Yeshua's mark and die by antichrist's hands! (Matthew 16:25 For whosoever will save his life shall lose it: and whosoever will lose his life for my sake shall find it. Mark 8:35 For whosoever will save his life shall lose it; but whosoever shall lose his life for my sake and the gospel's, the same shall save it. Luke 9:24 For whosoever will save his life shall lose it: but whosoever will lose his life for my sake, the same shall save it. Luke 17:33 Whosoever shall seek to save his life shall lose it; and whosoever shall lose his life shall preserve it.)
1260 days after the 23rd of September takes them to the 6th of March 2021 which happens to be the Shabbat Parah which is the red heifer sacrifice for the acceptable purification of a new temple! (Numbers 19:9 And a man that is clean shall gather up the ashes of the heifer, and lay them up without the camp in a clean place, and it shall be kept for the congregation of the children of Israel for a water of separation: it is a purification for sin. ) It is at this time also the son of perdition tries to kill Israel with a flood! Anyone ever heard of the age of aquarius? That same day the moon is in "aquarius" the star sign that shows the flood. I suspect it will be that day the son of perdition will break the Euphrates dam or find some other way to cause a flood but God protects Israel and will the Earth to swallow up the flood most likely by way of a great earthquake.
Exactly 1290 days (Daniel 12:11 And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days. 12:12 Blessed is he that waiteth, and cometh to the thousand three hundred and five and thirty days. )from then will be the 16th of September 2024 just before all the final Feasts of Yom Kippur which Yeshua will fulfil at that time but take it to the 1335 days of Daniel's prophecy at the end and see you arrive at Shemini Atzeret which is the eight day after Succoth(the Feast of tabernacles) which will be fulfilled at that time as His final Feast to be fulfilled. At all these dates signs are in the Heavens that can already be seen now in stellar software such as stellarium. Seek and you shall find!
From the day Shemini Atzeret is fulfilled the Lord's 1000 year reign will begin and all things will be restored as written.
Realise that if it is you who have been given this information by the Holy Spirit you are among the chosen few! (Daniel 12:10 Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand. )