I am an existing user of Ceridian Dayforce and my organisation users it for time tracking of the employees. Though I haven't attempted the integration of Dayforce with ServiceNow yet, however I assuming the integration should be straight forward as the REST APIs from Dayforce are already in place https://docs.merge.dev/integrations/hris/ceridian-dayforce/provider-interactions/
You might need to create some custom actions inside the flow designer and a script include to hit the API end points and GET, PUT, POST, PATCH methods provided by Dayforce to call a specific webservice method. This should be no different then the other API integration done via RestMessage_V2 API.
