expiration on limit orders

I would like to know about expiries on limit and stop orders? PlaceLimitOrder(TradeType, Symbol, Volume, targetPrice, MyLabel, StopLossPips, TakeProfitPips, Expiration); If I understand it correctly Expiration comes last and what is exacrtly the frame of calculation hours or minutes? Say I wanted a limit order to have a 1hr expiry would the code be? PlaceLimitOrder(TradeType, Symbol, Volume, targetPrice, MyLabel, StopLossPips, TakeProfitPips, 1); or PlaceLimitOrder(TradeType, Symbol, Volume, targetPrice, MyLabel, StopLossPips, TakeProfitPips, 60); or do we declare it as a variable?