One of the qualities that today's employers emphasize, and that prospective job seekers look for, is an emphasis on work/life balance. Some people take this to mean that every workday ends at 5 pm on the dot, end of story.
While many companies are sensitive to people's work/life balance, there is a reality, especially when you are new to a company.
As a new employee, it will take some time to learn the ropes. Even if you have been in an industry for a while, every company handles things differently. When you start a new job, you also may be starting just as the department is in the middle of a project with a looming deadline. The work needs to be done regardless of where you are in the company learning curve.
The first few months of a job are crucial for proving to your new bosses that they made the right choice in hiring you. Creating the impression of dedication to your job should be your priority during this time.
Extra time is not always necessary, and your hours may depend on the company culture. In some places, once 5 pm hits, the place might empty quickly. For some, being the new guy or low man on the totem pole means 5 pm is a coffee break.
As the people leave for the day, they may kid you with, "I've done my time." The important thing with that is that they are still there and now it is your turn. Look at it as your initiation to being one of the gang. In a few months, you may be saying the same thing to the next new guy. Putting in the time builds camaraderie since everyone knows you are taking the position seriously.
Depending on your job and your industry, you may have a season where you are much busier. Tax accountants have annual deadlines, and the months leading to those deadlines will require more time. Some departments, such as the Information Technology teams, are more project-based. A project timeline will mean more hours to keep the project on track. Regardless of your time in the company or your level of experience, these instances call for an "all hands on deck" approach.
Most companies recognize how different jobs and departments have different patterns. Many companies are taking these patterns into account when they discuss work/life balance and try to make it up to employees in different ways. Sometimes they make it up by buying lunch. Some companies may give comp time for long hours. Some companies just know that long hours are a fact of the job, and sometimes the employees have to realize that, too.