At the moment Route 53 does not support querying of last timestamp of DNS record update

In some DNS servers, we are able to query the last timestamp of the DNS records update using a "serial" attribute. For e.g.:-

*************
C:\>nslookup -q=SOA example.com
Server:  homeportal
Address:  192.x.x.x

Non-authoritative answer:
example.com
        primary name server = ns1.example.com
        responsible mail addr = hostmaster.ns1.example.com
        serial  = 2015010703
        refresh = 10800 (3 hours)
        retry   = 3600 (1 hour)
        expire  = 604800 (7 days)
        default TTL = 600 (10 mins)
**************

The above serial refers to the date and the number of updates done on that particular date (2015/01/07 and update # 3)

The above query does not work for a domain hosted on Amazon Route 53. The returned serial # is "1". Also, currently, Route 53 does not support CloudTrail so api calls to Route 53 do not get recorded. So the only way is to actually log a ticket with AWS Route 53 team and get the last DNS record update time stamp.