Metafield sort by date and time not visible on sorting page (Dawn theme)

[mikmokmuk]

Hello there, 

For a Shopify site we are making, we've assigned a date and time metafield to each product release. I wanted to know if there was a way to sort these on the product grid base on that metafield. 

We are using Metafield Manager for our metafields and in the filters page you can't find it (see screenshot).