This module may be used to convert Oracle date and timestamp values into
DateTime objects. It also can take a DateTime object and produce a date
string matching the NLS_DATE_FORMAT.

Oracle has flexible date formatting via its NLS_DATE_FORMAT session
variable. Date values will be returned from Oracle according to the current
value of that variable. Date values going into Oracle must also match the
current setting of NLS_DATE_FORMAT.

Timestamp values will match either the NLS_TIMESTAMP_FORMAT or
NLS_TIMESTAMP_TZ_FORMAT session variables.

This module keeps track of these Oracle session variable values by
examining environment variables of the same name. Each time one of
Oracle's formatting session variables is updated, the %ENV hash must
also be updated.