If you're asking for a decade (which this question is), there is surely no point giving the answer – or, more specifically, the leeway – in years.
If asking for a decade, there should be no real need to give leeway in any case; except that in this particular case, to give no leeway would penalise those who erred on the early side.
The best solution would surely have been to ask for the year and allow nine or ten years either way.
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