The other day, a friend and I got into a discussion about what I know is a common dilemma. She'd negotiated a schedule that allowed her to leave work at a reasonable time. She was putting in the hours (she came in early) but all the "cool kids" in her office worked late. After 5 p.m., the place took on more of a social vibe, and by leaving, she sensed she was missing out on the relationship-building aspect of work that not only makes the office more fun, but can boost you up the ladder.
So what should she do?
She'd hit upon this truth: In the workplace, not all hours are created equal. You can do your work perfectly well, but the more we see people, the more they stay in our minds. We also want to work more with people we have fun with, and fun seems most likely to happen outside traditional 9 to 5 hours. Sometimes that's because you're out grabbing drinks together, but sometimes it's just because everyone's ordering in dinner and shooting the breeze. In this woman's case, she wanted to see her kids before they went to bed, but there are lots of other reasons people wind up facing this dilemma. Trains leave at certain times. People have awful commutes and need to leave to beat the traffic.
Fortunately, there are ways to solve this problem. The first--as I sometimes sound like a broken record about--is to think in terms of 168 hours (a week), not 24 (a day). No, you're not going to work until 6:30 p.m. every day if your negotiated schedule allows you to leave at 4 p.m. But it wouldn't kill you to do it once a week or so. That way, people see you as part of the after-hours crowd fairly regularly. If you want to hold your hours constant, you can leave a little earlier on Fridays, or hit the gym some morning, and come in a little later.
You can also schedule social work events at times that are convenient for you. Planning is a pain for everyone, so taking on that task will score you points, and if you prefer office picnics that families can attend, or department volunteer projects that happen during the work day, you can make sure they happen. You can also create non-work social events. Throw parties, and invite the colleagues you actually like. Throw good enough parties and they'll seem like a lot more fun (and perhaps more exclusive) than shoveling sushi at 7 p.m. with whoever's still at the office.
And finally, be sure to create one-on-one time with colleagues so you can have the conversations that make so much happen. If you leave early, you might think you should work through lunch to show you're as dedicated as everyone else. Resist that temptation. Instead, grab a colleague and head to the deli together. Never go out for coffee alone. You can create lots of chances for people to see you, no matter what time you walk out the door.