@chrisfr1976 Thank you for sharing. This helped me it seems it was an issue with my conditions using the ev.title.search(‘string’) solved my issue. eventTransformer: (ev) => { if (ev.calendarName === "Trash") { const trash = []; ev.color = 'gray'; if (ev.title.search('Altpapiertonne') > -1) { trash.push("fa-solid fa-trash trash-blue") } if (ev.title.search('Gelbe Tonne') > -1) { trash.push("fa-solid fa-trash trash-yellow") } if (ev.title.search('Biotonne') > -1) { trash.push("fa-solid fa-trash trash-brown") } if (ev.title.search('Restmülltonne') > -1) { trash.push("fa-solid fa-trash trash-black") } ev.symbol = trash; if (trash.length === 0) { ev.symbol = []; ev.color = "none"; } } return ev; } } } [image: ycfzpQ5G]