If u can't remember the perfect year, then learn it's century and decade. It'll be a lot easier. Like the date 1945 - 20th century, 4th decade.It'll fetch u marks.
After u 've learned a few dates, connect them. Like if a particular thing 'a' happened on 1865, learn an event that happened like 10 yrs later, for eg. 'b' happened in 1875. U 'll not forget the dates anymore.