International deadline planner
Working days, hours, and the deadline are only what you enter. Contracts, statutes, and bank settlement times are not inferred.
Country selects holiday data, the timezone is an IANA zone, and the page language is the locale. Those three are separate.
Holidays: offline date-holidays (code ISC, data CC BY-SA 3.0). Offsets: IANA zones via the runtime tzdb.