Possible Clues:

• Like months when oysters are not in season
• Like May through August, literally
• Like May through August, unlike the other months of the year
• Like inopportune months to eat oysters
• Like months when oysters are out of season
• Like poor months for oysters, it's said
• Like Harvard Yard, in a Boston accent
• Like 'Harvard Yard,' as spoken by some locals
• Like "Harvard Yard," as spoken by some locals
• Like the spelling of oyster-abstaining months