If your sim doesn't go to work at the right time due to events, you can go into the work panel and click on the desk icon, it should say 'go to work' if your sim is a little late and it will queue your sim for work. I've had to do that when one sim was off lot and I was controlling another sim at the house, I noticed the off lot sim hadn't gone to work, so I called her home and then manually sent her.