The 1260 days and the 490 days are separate, non-overlapping time periods that come from separate prophecies in Daniel.
The 490 Days
24Seventy 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. 25Know 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. (Daniel 9:24-25, KJV)
The 1260 Days
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. (Daniel
12:7, KJV)
The 1290 Days
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. (Daniel 12:11, KJV)
The 1335 Days
Blessed is he that waiteth, and cometh to the thousand three hundred
and five and thirty days. (Daniel 12:12, KJV)
The 490 days (70 weeks) are the first of the 2300 days of Daniel 8:14, whereas the 1335 days of Daniel 12 are the last of the 2300 days. The 1290 comes at the start of that 1335, and the 1260 begin 30 days later. All of these "days," of course, represent years.
The 490/2300 began in 457 BC. The first 7 weeks of this, i.e. 49 years, was the period of time during which the Second Temple was being built. As the Jews told Jesus, it took 46 years to build it, and it was forced to a stop for legal hassles for several years.
The 69th "week" of the 70 brings us to AD 27, the year in which Jesus was baptized and began his ministry. This starts the final "week," the one which is split in half. In the middle of that week, Jesus is crucified. The end of that week is AD 34--the time when Stephen is stoned and the Gospel truly begins to spread among the Gentiles. This was the end of the Jews' grace period (forgiveness), according to Jesus' reiteration of the 490 prophecy.
Jesus saith unto him, I say not unto thee, Until seven times: but,
Until seventy times seven. (Matthew 18:22, KJV)
"Seventy times seven" is 490.
All of these are fulfilled.
These prophecies have already been fulfilled, the longest one reaching to AD 1844. At the end of this longest time, another prophecy comes, found in Revelation, which ends any further declaration of times.
5And the angel which I saw stand upon the sea and upon the
earth lifted up his hand to heaven, 6And sware by him that
liveth for ever and ever, who created heaven, and the things that
therein are, and the earth, and the things that therein are, and the
sea, and the things which are therein, that there should be time no
longer:" (Revelation 10:5-6, KJV)
This "time no longer" means that no more prophetic times will be given or applied. (It obviously does not mean that time itself should cease to exist, as some have interpreted--that would be entirely unreasonable.)
The "time no longer" means that for the end-time events, we will not have a prophetic timeline to guide us. No one will know when probation closes, when the seven last plagues will fall, or when Jesus will return. We are told to "expect" these events as that of the coming of a thief in the night: a thief does not announce his arrival ahead of time. Even Jesus himself claims not to know when these times will be.
But of that day and that hour knoweth no man, no, not the angels which
are in heaven, neither the Son, but the Father. (Mark 13:32, KJV)
If Jesus does not know these times, we would be more than presumptuous to think we could know them.
Conclusion
Jesus made it clear that we will not know the time of his coming, even apparently excluding himself from this knowledge. While we are not in ignorance that the day is approaching, we do not know "the hour."