SDX Commodities & Energy automatically inserts the expiry date and/or underlying contract for each instrument. It does this according to the market convention for the current commodity and instrument type.
That is, after you use a duration shortcut, contract shortcut or electricity contract shortcut in the relevant field (this depends on the instrument type and can be the Expiry field, the Underlying Forward Contract field (for electricity only), the Underlying Contract field, the Shortcut Schedule field, the Swap Term field, etc.), the system then uses this information together with the market conventions to set the actual expiry date and/or underlying contract.
What is the market convention?
For:
Most deals, the expiry date is simply the exchange date for that month.
An Asian and Asian strategy, for all commodities except for precious metals the market convention is to use the last business day of the month as the expiry date.
For a vanilla-based option, a bullet-based option, a barrier, binary or European binary on NBP UK Natural Gas, the market convention for the expiry date is now set to the fifth to last day of the month prior to the expiry month. If this day falls on a non-business day (i.e., on a weekend or holiday) then the expiry is set to the closest preceding business day instead. So if you enter Oct 2009, five days from the end of the preceding month (September) is 26th of September, which is a weekend day. So instead the preceding date (25 September) is used.