'Established' in the Bible

Then at the end of the training period that the king had established, the chief officer brought them in before Nebuchadnezzar.

So they approached the king and asked, "Didn't you sign an edict that for the next 30 days if anyone prays to any god or man, except to you, your majesty, he would be thrown into the lions' pit?" The king responded, "The decree has been established, in accordance with the laws of the Medes and Persians that can't be repealed."

There will be 1,290 days from the time the regular burnt offering is rescinded and the destructive desolation established.