Hi,
Less than is correct becuase phrase "in less than" is a continuing action...for example :In less than 35 years birds were planning, just as it took less than 35 years two different meanings. apply to a sentence to your self. Less than means the birds were not expected to migrate, in less than would indicate a time period already set from the past continuing in the present....not the case in this setence...thanks

moneyman...
i thing that the action itself (in the underlined setence/phrase) is in the past.