Sorry I wasn't clearer but I meant that both crusade and heresy would likely have taken place between 000 and 070. If Macharius was inspired to his crusade by events at Mount Amalath and that occurred at the start of M41, he couldn't have begun until late in 000.M41.
Given that it's supposed to have been the largest crusade of the 41st millenium, I'd allow 5+ years to gather the troops, the seven years for the crusade itself and a year or two before the generals kick off their heresy. Which would give a 30-odd year life for the heresy or you just add 70 years to the above, so that the heresy ran from c014-084.M41
Alternatively, everything you have been told is a lie! I'd never even heard of the Macharian Heresy until this thread. Somewhere there's a quote from General Sejanus' biography of Macharius, describing the Lord Solar's breakdown when he called an end to the crusade. So I was a little surprised to hear that he became a heretic. I've had a quick hunt for the quote but all I can say with certainty is that it's more recent than WD272, or else in the 3rd edition of the guard codex (as my copy's MIA).