Ajv - validate utc data with age requirement

I have a field that stores an integer donating date of birth in UTC time:

utc_millisecond: {
    type: "integer",
    minimum: -5361984000000, // 1800
    maximum: 2527290061000, // 2050
}

The problem with the above schema is that, the values are static while time always goes forward.

There is a requirement that the dob_milliseond value translates to an age that is greater than 18 and less than 100.

How do I further specify this above requirement?

EDITED:

I already have a function that converts utc milliseconds to age:

function utc_to_age(utc) {

}

So I just need to integrate this custom function into the ajv schema validator

I figured out a way:

  ajv_inst.addKeyword({
    keyword: "dob_utc_int",
    validate: (schema, data) => {
      if (!Number.isInteger(data)) {
        return false;
      }
      const age = utc_to_age(data);
      return schema.max_age >= age && schema.min_age <= age;
    },
    metaSchema: {
      // compilation error
      // schema to validate keyword value
      type: "object",
      properties: {
        min_age: {
          type: "integer",
          minimum: 18,
          maximum: 150,
        },
        max_age: {
          type: "integer",
          minimum: { $data: "1/min_age" },
          maximum: 150,
        },
      },
      required: ["min_age", "max_age"],
      additionalProperties: false,
    },
  });

Now just need to have it print error messages.