By how many minutes are you late to work in "Half-Life"?

In Half-Life, you are late to work by 30 minutes. This can be inferred from the beginning of the game when the main protagonist, Gordon Freeman, arrives at his workplace, the Black Mesa Research Facility, after a catastrophic event has occurred. The event in question is the Resonance Cascade, which caused dimensional rifts and unleashed hostile creatures into the facility. Since Gordon Freeman was scheduled to start his work shift at the time of the incident, it can be assumed that he is approximately 30 minutes late as he arrives just after the chaos has already unfolded.