custom start/end time not working

Hi Guys,

I am running version ganglia version 3.6.0-1 and the web version 3.6.2
which uses rrdtool to build its graphs.  Looks like if I use the
predefined time tabs for "Last - hour/2hr/4h/day/week/month/year/job"
my stacked graph shows up just fine.  However if I add a custom time
range with the start time being before the end time the stacked graph
does not display and I get the following in the apache error logs:

ERROR: start time: There should be number after '-'

The link to the broken image shows:

http://{ganglia-web}/stacked.php?m=load_one&c=rescomp&r=custom&st=1467142510&host_regex=

Looks like potentially the correct start time is not being generated
from the web ui and passed to rrdtool?  Am I missing something here?
Has anyone seen this issue and if so how can I fix it?

Thanks in advance for your help with this!