It's expected that you'll spend time with your girlfriend.
Stan and Pam have been together for a year and their anniversary is tonight, but Stan has a chance to meet with a high end client.
Stan wants to meet with the client.
Stan explains how important the meeting is to Pam, and they reschedule their dinner for the following night.
Stan gets out of the anniversary dinner by pretending that he's got the flu, and is able to meet with the client.
Stan closes a big deal with the client and is still able to celebrate his anniversary.
Stan will disappoint Pam and she breaks up with him.