false dawn 
noun
1A promising situation which comes to nothing: after so many false dawns, Britain was finally enjoying an export-led boom...
- The past five years have been peppered with false dawns from the two inquiries by outside police forces, which brought her no satisfaction, to the first inquest in 2002, which devastated her with its open verdict.
- It all looks very promising - yet false dawns and fresh starts are common in Africa.
- There must not be any more lost opportunities or false dawns.
2A transient light which precedes the rising of the sun by about an hour, commonly seen in Eastern countries.Overhead, the final wave of charges was flooding in, an iridescent ribbon of gold-red light that broke a false dawn over the island....
- The huldre's sobs are dying down when false dawn lights the sky.
- This time, I was the one to let Brock sleep, waking him only an hour or so before false dawn.