Geçen yıl üç ay boyunca denizdeydi. - Last year, he was at sea for three months.
Jeff bir iş bulmadan önce üç ay boyunca kaldırımları arşınlamak zorunda kalmıştı. - Jeff had to pound the pavement for three months before he found a job.
The period of duration from the same date of one month to the same date of the next month, and thus can be 28, 29 during a leap year, 30 or 31 days long. For example the duration from 21st January to 20th February