Just as humans follow their own calendar of rituals and events, the biological clocks of animals coordinate their physiology and anticipate rhythmic changes in the environment. Over the course of the year, many of the great natural events happen with clockwork precision.

This landmark six-part documentary series charts the planet’s most spectacular events of migration, rebirth and transformation. Over the course of a turbulent and perilous year, we witness how finely tuned creatures face the Earth’s seasonal patterns as they become more extreme, less predictable and dangerously unreliable.