Agenda webservice

request to build an online webservice. the webservice exists of an agenda tool that should work for multiple type of entries, multiple resources and users. It should have different views, week, day, month etc. the webservice should work fast, register every change of data instantly (like in google calendar it is possible to move an meeting with the mouse and drop it at another time slot), and give the possibility to undo last change. it should save all data on an online server, but the tool should continue to work offline, when internet connection is lost, when internet connection is on again it should synchronise the changes made offline and online. The agenda should be visible/open for external parties (users with accounts) to schedule meetings directly in the agenda. the webservice should be build with a clear architecture, well structured, modular build, design separate from functionality, with secured connection, it should support multiple languages. As owner/provider of the webservice it should be possible to analyse usage statistics. design, positioning and images like images, logo's and icon's will be provided, but the actual programming of the design must be taken care of. First please propose a project plan and what programming languages are most suitable for this webservice. Secondly please provide me with an estimate in budget and time (specified). Also please provide me with the 3 best reference links to webservices your company has build. After selection of the developing company based on the requested information we will provide you with a full detailed requirements document.