VueJS reactive Date object
You are modifying the date object in place in which case Vue can not detect the changes, create a new date object instead:
https://jsfiddle.net/13gzu8xs/1/
new Vue({ el: "#app", data: { date: new Date() }, methods: { inc () { this.date.setDate(this.date.getDate() + 1) this.date = new Date(this.date) // create a new date and assign to this.date }, dec () { this.date.setDate(this.date.getDate() - 1) this.date = new Date(this.date) } }})