presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/dayFromInterval
class DateTimeFunctions:    @Description("day of the month of the given interval")
    @ScalarFunction(value = "day", alias = "day_of_month")
    @SqlType(StandardTypes.BIGINT)
    public static long dayFromInterval(@SqlType(StandardTypes.INTERVAL_DAY_TO_SECOND) long milliseconds)
    {
        return milliseconds / MILLISECONDS_IN_DAY;
    }