It's supposed to be 180 days before the writ. It's the same in English as in French. I'm afraid I'm also confused as to whether they've made a mistake in the drafting.
They told me when I asked that question
about the wording of “de centre de scrutin dès la date de délivrance du bref”.
it may be that there's a drafting error. I thought that, but I was assured it was the same.