I secured a speaking slot at a fairly significant conference (more than 500 attendants). My previous manager was happy to cover flights and accommodation so I could speak at some conferences. The employer branding people were delighted as well.

More recently, my new boss has planned a lot of work in the coming weeks. They are against my missing one day at work. This direct boss approves vacations and budget ( travel expenses ). **How do I convince the new boss, this conference is more important than one day at work ?**

I've made the argument that:

* it is good for branding and potential talented hires.
* the company didn't have to spend money on sponsorship. Most
conferences have attributed sponsored speaking slots. I saved money.
The travel expense is a bargain compared to the sponsorship fee.
* the speakers have already been announced. What do I look like if my slot is removed?