Not sure about the difference between graduate schemes and graduate jobs (or direct entry jobs)? Have a look at the explanation in the first section on the graduate jobs page. These are advertised at different times of the year, with different timescales and recruitment processes.
Recruitment to graduate training schemes starts far in advance of actual start dates - so be prepared to think about what you want to do and apply early.
These jobs are advertised all year round by organisations of all sizes and in all sectors. The recruitment process is shorter than for graduate schemes; the employer may expect to fill the role within around six weeks of advertising.
Depending on the type of company you are hoping to work for, the time scales for placement years and summer internships are likely to be similar to those for graduate schemes above. Schemes with the "Big Four" professional services companies are likely to close by December/January, whereas internships and placements with smaller organisations or in other sectors have later deadlines.
Summer internships offered by the University of York's Student Internship Bureau are advertised from the beginning of April.
Find out more about placement years and internships on our Internships and work experience page.