In most cases, your work history comes from your own knowledge of your employment, rather than as documentation from an employer, and consists of date on which you held the position and your responsibilities and accomplishment during that time. However, it may be possible to contact the human resources department of the company to find exact start dates, end dates and job descriptions.
When writing a resume, it is important to provide a clear and accurate description of all your relevant work history so that the employer understands your skills and experience. As you are the one creating your resume, you have full control over the wording and how you present the information, as long as it does not consist of lies or gross manipulations of the truth. You should begin with the basic facts of the job, such as your official title and the months and years you started and left. If you don't have this information, email the human resources department from the company with your name and employee number, if available, and request it.
Work history also needs to explain the nature of the job and how it relates to your current career path. Highlight your most significant accomplishments and the important aspects of your daily tasks to show an employer why you qualify for the new job. Use an active voice and focus the actions you took at the job to create a positive picture of your skills.