JSD calendars are useful for enforcing non-24hr hours of operation. However, they fail to take account of when an organisation operates in a location with daylight saving time.

For instance a contract may specify 9am - 6pm for support. However the server time does not change to reflect daylight saving time. Therefore for part of the year the SLA calendar will not align with the contract hours.

I discussed this at Summit 2016 with Vidhu, Lingbo and Adriana. Please contact me direct for a PoC.

A partial workaround is to use the created time to determine which SLA calendar to use and define summer and winter calendars. I am about to publish a blog post on this workaround and will add a comment when I have the url.