Trying to connect a HTML5 date input with date model - vue.js

Question

I have an HTML5 date input element like this:
<input type="date" />
if you choose a date in this input a string will be the value, for example:
"2018-12-31"
In my model I want the date to be presented as the following string:
"2018-12-31T00:00:00.000Z" and not the simplified string.
How do I make sure that the date in my model keeps the correct format? I tried using a computed but since I am in a loop this time I cannot use them.
{{eventDate.date}}
<b-form-input
v-bind:value="eventDate.date"
v-on:input="eventDate.date = $event.target.value"
v-bind:id="'event-day-date-' + index"
size="sm"
type="date"
placeholder="2018-12-31"
>
</b-form-input>
As you can see here the eventDate.date is a long string but the input needs the format YYYY-MM-DD. I need to convert it to and from this format some way.

Answer 1

You could use a filter:
filter: {
dateToString(date) {
return date.toString().substr(0,10)
}
}
and then update your template
:value="eventDate.date | dateToString"

Answer 2

This is what I ended up using:
<input
v-validate="'required'"
v-bind:name="'eventdate-' + index"
v-bind:value="eventDate.date | dateToString"
v-on:input="eventDate.date = $event.target.value + 'T00:00:00.000Z'"
v-bind:id="'event-day-date-' + index"
class="form-control form-control-sm"
type="date"
placeholder="2018-12-31"
/>