Good timing! :) We just released that feature yesterday to Outlook on the web (outlook.office.com). Under Settings -> Calendar -> Events & invitations, you should see the option. If you have set it in the Windows client, it should be automatically set for you in the web.
@Julia Foran Hi Julia - Where is this feature? Apologies but I do not see it - here is a screenshot for reference: I am going to go check the Windows client, but I would prefer to be able to set it from the web.