If you need to sortBy or apply a customRanking attribute based on a date in Shopify, you will find that the date formats on your product data are alphanumeric strings. This is the format that is provided on the product data that we request to Shopify.
Because Algolia doesn’t interpret dates as ISO 8601 strings (such as “2008-09-15T15:53:00”), you must convert your dates into Unix timestamps (numeric values such as 1221486780) before sorting them. For more details about this you can refer to this documentation.
When you need to enrich your products data with an additional attr/value, you can implement metafields. On this case you can use the number type for this purpose. Then, you will be able to add this as a sort order directly on the plugin:
Algolia plugin > Search options > InstantSearch > Sort orders