Google has follows-the-sun on-call rotations for large rotations, so this hit the UK team just after lunch.
Ah so the rotation rotates to match the current rotation. Very smart.
The sun never sets on the Google empire
I like the mental image of this being a very precise matching -- as the sun traces across the sky, the responsibility of on-call passes from desk to desk, town to town, country to country; two engineers on a boat in the Atlantic race to keep up with their rotation...