Q: This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
Passage: On July 17, 2012, the CRTC approved the shut down of CBC's analogue transmitters, noting that "while the Commission has the discretion to refuse to revoke broadcasting licences, even on application from a licensee, it cannot direct the CBC or any other broadcaster to continue to operate its stations and transmitters." On July 31, 2012, at around 11:59 p.m. in each time zone, the remaining 620 analogue transmitters were shut down, leaving the network with 27 digital television transmitters across the country, and some transmitters operated by some affiliated stations.
A:
When did the CRTC order the shutdown of the analogue transmitters?