Final answer:
The statement is true; time zones are roughly based on 15-degree meridian intervals, but practical adjustments lead to varied boundary lines that deviate from this ideal standard.
Step-by-step explanation:
The statement that 24 time zones are roughly centred on meridians at 15-degree intervals is true. The concept behind time zones is based on the Earth's rotation and the division of the Earth's equator into 360 degrees. Every 15 degrees of longitude represents a difference of one hour in local time zones, as the Earth rotates at a rate of 15 degrees per hour and completes a full rotation in 24 hours.
While this 15-degree interval system is an ideal representation, various practical adjustments are made to time zone boundaries due to political, administrative, and geographical considerations. These adjustments can result in the boundaries of time zones not strictly adhering to the 15-degree width. Notably, the continental United States has four main time zones, but they do not align perfectly with meridians due to state and regional boundaries.
In special cases such as China, despite spanning five geographical time zones, the entire country operates on a single time zone for uniformity. This illustrates how time zones are adjusted for practicality rather than strictly following geographical lines.