password policy options

Hi I'm trying to generate a delimited file for import with dsimport from code and I want to set some of the PasswordPolicyOptions so I'm including that field in my delimited file. Specifically, I want to set expiry times on (some) accounts. I exported one of my user's records to look at it as an example and I see there are a lot of field left as 0 like this: isDisabled=0 isAdminUser=0 newPasswordRequired=0 usingHistory=0 canModifyPasswordforSelf=1 usingExpirationDate=0 usingHardExpirationDate=1 requiresAlpha=0 requiresNumeric=0 expirationDateGMT=0 hardExpireDateGMT=1157050800 maxMinutesUntilChangePassword=0 maxMinutesUntilDisabled=0 maxMinutesOfNonUse=0 maxFailedLoginAttempts=0 minChars=0 maxChars=0 passwordCannotBeName=0 requiresMixedCase=0 notGuessablePattern=0 isSessionKeyAgent=0 So now I have a few questions: a) Can I omit unused options? (like isSessionKeyAgent) b) What's the difference between "usingExpirationDate" and "usingHardExpirationDate"? c) And between "expirationDateGMT" and "hardExpireDateGMT"? d) Do I have to use UNIX time? I have been looking through the Command Line Administrator's guide and found that very few of the fields in the delimited file are describe much and the password options aren't covered at all. I'm just shooting in the dark here, is there a better source I should be looking at?