In a command line terminal you go to directory /home/pi/pimatic-app/node_modules/pimatic-sunrise
Edit the file sunrise.coffee with nano or whatever you want with the 2 changes below.
Save the file and restart Pimatic.
Change the following
line 95
return Promise.resolve @_transformTimezone(@eventTimes[attribute.name]).toLocaleTimeString()
into
return Promise.resolve moment(@_transformTimezone(@eventTimes[attribute.name])).format('HH:mm:ss')
and line 105
@emit attribute.name, @_transformTimezone(@eventTimes[attribute.name]).toLocaleTimeString()
into
@emit attribute.name, moment(@_transformTimezone(@eventTimes[attribute.name])).format('HH:mm:ss')
It is reformatting the values of the sunrise attributes. You should test the rules behaviour