presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/addFieldValueTimestamp
class DateTimeFunctions:    @Description("add the specified amount of time to the given timestamp")
    @LiteralParameters("x")
    @ScalarFunction("date_add")
    @SqlType(StandardTypes.TIMESTAMP)
    public static long addFieldValueTimestamp(
            ConnectorSession session,
            @SqlType("varchar(x)") Slice unit,
            @SqlType(StandardTypes.BIGINT) long value,
            @SqlType(StandardTypes.TIMESTAMP) long timestamp)
    {
        if (session.isLegacyTimestamp()) {
            return getTimestampField(getChronology(session.getTimeZoneKey()), unit).add(timestamp, toIntExact(value));
        }

        return getTimestampField(UTC_CHRONOLOGY, unit).add(timestamp, toIntExact(value));
    }