For additional reading, we have addressed a similar question here: https://www.preplounge.com/en/consulting-forum/whats-the-best-time-of-the-year-to-apply-for-an-mbb-entry-level-position-908#a1781
Internship lenght and start period depend on the region and role you are applying for and it generally follows the calendar of universities. Internships are generally three or six months long but again, that varies from a few weeks to a year depending on the role and location.
I will refer to France in the following example:
- 6 month internships have two main starting slots:
- January: I would start applying from June of the previous year (the earlier the better for competition)
- July: I would start applying as early as January (same as previous, the earlier the better for competition)
- Summer internships generally starts in May/June (~3 months) you can apply starting January for the next year (same as previous, the earlier the better for competition)
You can move the calendar according to your geography to take into account the equivalent of Summer and Winter.
Feel free to reach me if you have any additional question,