I am reading the NORTH ATLANTIC OPERATIONS AND AIRSPACE MANUAL and I came across the following statement more than once during my reading:
The activation time of the westbound OTS shall be published as 1130z to 1900z at 30W.
The activation time of the eastbound OTS shall be published as 0100z to 0800z at 30W.
You can find this quotes at page 175 of the link provided above.
Here is my question: if the activation times are expressed as ZULU time (therefore as UTC), why is it specified at 30W? As far as I know a ZULU time is referred to the Greenwich meridian and therefore at 0W. To me it sounds quite contradictory to express an UTC time by specifying a longitude different than 0.
What am I misinterpreting? What is the right interpretation of the quotes presented above?