The easiest way to do this is on a global level. You need to modify the OOTO agent in the template to have the schedule you want. You then need to refresh the design of everyone’s mail file from that newly modified template. After you do that, though, the agent will be signed by you. The next time people turn on the the OOTO agent, they simply need to make sure they change the dates or text so that it updates the agent with their name (so it comes from them). This happens 99.9% of the time anyway, but it is something to note.