Now if by time you mean when is the best time to look for a bew job, then that’s a different story. If you are not happy with the work you are doing, not just because your boss is “mean”, than it maybe time to start looking for a new job. You will always be happy doing the work you love doing and will not feel like a job.
If you are close to graduation from any school and or are looking for another job, Now is the time to start looking. Always allow yourself enough time to get your information together and then start submitting resumes and cover letters. Make sure that if changing jobs you give the 2 weeks notice required by most companies.