I think his hiatus used to run late, possibly even into October
Some time ago I set out to answer that very question, simply by going back and registering the beginning and end dates of his hiatus. In the 5 years before 2012 he invariably left late June, to return (variably) in September:
2012, left 03/29, returned 09/??
2011, left 06/29, returned 09/13
2010, left 06/28, returned 09/03
2009, left 06/27, returned 09/03 (MFIF closed on 08/04, Hal registered @ FTMF on 09/03)
2008, left 06/27, returned 09/08?
* We're all doomed! [Lounge, Page #7]
2007, left 06/26, returned 09/12
Belgian Pale Ales [Lounge, Page #14]
2006, left 07/12, returned 09/22
Who's Hot? Who's Cool? [Lounge, Page #20]
Hal uses his handle elsewhere too, but so far his hiatuses there have matched the ones at FineTunedMac and MacFixIt. This year's starting date was 3 months early, and I hope his return will not be 3 months late as well. Most importantly, I hope he's well, and not too discombobulated with our attention here...
*)
the MFIF Archive search function seems limited to 200 returns; shows last post listed in Summer.