IELTS, the International English Language Testing System, is designed to assess the language ability of candidates who want to study or work where English is the language of Communication. 

IELTS is offered up to four times a month in more than 125 countries. Tests are usually on Saturdays or Thursdays. 
You can book your test date basing on the availability of seats. Of course, you should also decide how well prepared you are for the test. This is actually vital consideration for deciding on the test date.

There are two modules to choose from â?? Academic and General Training.

The Academic module is for candidates wishing to study at undergraduate or postgraduate levels, and for those seeking professional registration

The General Training module is for wishing to migrate to an English-speaking country (Australia, Canada, New Zealand or UK) and for those wishing to study or train at below degree level.

Both modules cover all four language skills â?? listening, reading, writing and speaking. Everyone takes the same Listening and Speaking tests. There are different Reading and Writing tests for the Academic and General Training modules.

The Listening, Reading and Writing tests must be completed on the same day. There are no breaks between the three written tests. The Speaking test may be taken up to seven days before or after the other three tests.