Time zones and Unix time for real workflows
Unix timestamps are common in APIs, logs and databases, while named IANA time zones are essential when a human wall-clock time needs daylight-saving rules. Calendar arithmetic and elapsed duration are separate problems.
Use Date Calculator to move a date by years, months, weeks or days; Time Duration Calculator for elapsed clock time; Unix Timestamp Converter for epoch values; and Time Zone Converter for the same instant across named locations.