If you count my "real" job, it was a week.
If you count the family business, it was literally minutes!
Father ran a newsagents shop. He died on the way to open up the shop one morning at 5am. I got a phone call at 6am, and me and my brother went to open up the shop, mark up the papers for the paperboys, etc., and then keep the shop open daily thereafter between us.
On the day of his funeral, we did the morning papers, then closed early for the funeral, then re-opened for the evening papers!
The shop would have lost all it's customers and newsrounds if we'd have closed it for a few days, so we had to keep it open and operating in order to sell it.
When my mother died many years later, it was a Sunday, and I was back in my office on Monday - self employed accountant and I had VAT returns, wages, etc to do, so clients would have ended up being fined for late submissions and they'd not have been able to pay their staff if I hadn't gone in to work as normal.
Needs must when you're self employed!