What to be deemed an arear of rent under this Act.

    Any instalment of rent which is not paid on or before the day when the same is payable according to the pottah or engagement, or, if there be no written specification of the time of payment, at or before the time when such instalement is payable according to established usage, shall be held to be an arrear of rent under this Act, and unless otherwise provided by written agreement, shall be liable to interest at twelve per centum per annum.