level 1 inputs

sir this is the last paragraph under level 1 inputs paragraph mentioned in the technical article on IFRS13. can you pls explain this, i don’t understand this:

“An alternative method may be used where it is expedient. The standard sets out certain criteria where this may be applicable. For example where the price quoted in an active market does not represent fair value at the measurement date. An example of this may be where a significant event takes place after the close of the market such as a business reorganisation or combination.”