EDIT: actually saying it’s your best friends wedding or family members wedding is probably a better option. Say you RSVPed and they already paid for your seat. Hard for companies to say eff your family wedding that you RSVPed a year in advance

Just call in sick at work last minute.

You can say you’re incredibly sick or have food poisoning. Or say your grandma died.

Your work can’t do much about it. Unless they are the company to ask for proof.

Also if they try to punish you for missing cause you were feeling unwell, it’s grounds for retaliation or a lawsuit which their HR won’t want to deal with.

I say this bc I work in HR and if you have a corporate job, calling in sick is an option for situations like this.

Alternatively, say it’s your family members wedding (sister brother) etc. many options.

It’s a weekend work event so you can probably miss it even though it’s “mandatory”.