“For 2,300 evenings and mornings.” The Old Testament always reckoned time by “evening and morning,” not by “morning and evening” as we do. This makes perfect sense because the Hebrew day started at sunset not at midnight like our Western days do. [For more on the hours of the day and watches of the night, see commentary on Mark 6:48].
The period of time covered by 2,300 days is six years and almost four months. This is longer than the Antichrist will have his full power in the book of Revelation (he will wield his full ungodly power for three and a half years). Daniel 8:14 gives us the end of the 2,300 days, which is when the sanctuary is restored. Historically, that was in December of 164 BC. The likely start date of the 2,300 evil days was when a legitimate High Priest of Israel, Onias III, was murdered. The cause of the murder was jealousy and suspicion between Menelaus, the High Priest who had come to power by bribing Antiochus, and Onias, and after Onias was murdered the relationship between Antiochus and the Jews went quickly downhill.
There are scholars who think that the 2,300 evenings and mornings refer to 2,300 sacrifices, one in the evening and one in the morning, which would occur over a period of 1,150 days, but this is short of the three and a half years the Antichrist will be in power in Revelation (but it can be made to fit events in Antiochus’ reign). Nevertheless, to us the stronger position is that the 2,300 evenings and mornings means 2,300 days.