The Bill provides for a referendum on EU membership to be held on any date up to 31st December 2017. The referendum would be triggered by an Order made by the Secretary of State though there is a requirement for the Order to be 'laid before, and approved by a resolution of, each House of Parliament.'
Clause 3(3) enables the Order to modify or amend 'this Act or another enactment.' Henry VIII is alive and kicking - (see views of Lord Judge CJ - Henry VIII clauses). Clause 3 reads:
Conduct of the referendum and further provisions
The Bill has been introduced at this time for party political reasons with 'Eurosceptic' MPs worried about the success of the UK Independence Party (UKIP) in the recent local government elections. The Eurosceptics are annoyed that a referendum Bill was not included in the recent Queen's Speech. For more of the political detail see, for example, The Guardian and for details of Britain's financial contribution to the EU - see Budget Information.
The draft legislation has been published by the Conservatives so that it can be brought to the Commons for debate by one of the party's backbench MPs in the form of a private member's bill, rather than one sponsored by the government.
Addendum 16th May:
The Guardian - Cameron snubbed by 114 Tory MPs over absence of EU poll in Queen's Speech
BBC - EU Referendum: Tory MP will take forward bill