Q: I know what ZULU (UTC) time is, but what’s the deal with “ZULU DATE”?
A: ZULU date is the calendar date at ZERO degrees longitude. ZULU, UTC, and GMT are all synonymous and do not change in summer or winter.
It is truly UNIVERSAL TIME COORDINATED, not matter where you are...even in outer space! At 0000Z the date advances. For the Pacific Time Zone in winter (PST) UTC is eight (8) hours ahead. And at 1600L (4:00 p.m.) every day a new UTC day begins. A UTC log entry or RADIOGRAM originated after 1600L (in the PST), must be dated the next day. At 2400L (midnight) the local date again matches the UTC date, until 1600L.