And he said unto me, Unto two thousand and three hundred days; then shall the sanctuary be cleansed. Dan 8.14
Dan 2 and 7 tells us that the world will be ruled by pagan powers and post that there will be judgement and the reigning will be given to the saints. But in those chapters we wont find how long it will take for the prophecy to be fulfilled.
Dan 8 repeats the prophecies of Dan 2 and 7 and also gives a timeline for the prophecies.
How long shall be the vision (concerning) the daily (sacrifice), and the transgression of desolation, to give both the sanctuary and the host to be trodden under foot? Dan 8. 13 (marginal)
Daniel is informed that it will be 2300 evenings and mornings (i.e., 2300 days) until the sanctuary will be cleansed.
Let us recap the sequence in Dan 2 and 7 to understand what is cleansing
Dan 2 = Babylon — Medo persia — Greece — Rome — mixed powers — Second coming — dominance given to the saints
Dan 7 = Babylon — Medo persia — Greece — Rome — Judgement
Dan 8 = Medo-Persia — Greece — Rome — sanctuary cleansed.
Comparing this three chapters we understand the sanctuary cleansing is related to second coming and Judgement.
In Bible we read there are two sanctuaries of God. The original is in heaven and its model in earth. The model in earth was a representation of the original sanctuary in heaven.
We dont have the earthly sanctuary anymore so the cleansing must be that of heaven. Also we learn from Bible that the earthly sanctuary do not have any significance post the death of Christ.
Was there a cleansing in earthly sanctuary which is symbol of the cleansing in heaven.
The sins of the saints which is Transferred to the Sanctuary will be Cleansed on the day of atonement. Whichever soul was found unworthy in the day of atonement will be removed from the saints.
We also read in Bible that the heavenly record book has sins of saints and sinners and the records of saints will be removed from the heavenly records during cleansing of the heavenly sanctuary.
Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; Acts 3. 19
Peters tells that the repented sins will be blotted out during the time of refreshing.
So when does the 2300 days (2300 literal years ) starts.
Dan 9. 24 Seventy weeks are determined (hebrew – cutoff)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.  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.  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.  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.
As the vision continues in Dan 9 an Angels informs that 70 weeks (490 literal years) is cutoff for Jews to reconcile with God and Messiah to be crucified.
This 490 years were cutoff from a longer period which 2300 years as both the time prophecies are one and same vision.
The 70 weeks prophecy started in 457BC when the degree to rebuild Jerusalem went into effect. At the end of 69 prophetical weeks Christ was anointed. In the middle of next prophetical week Christ was crucified and at the end of 70 prophetical weeks the probation for Jews was closed. (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,)