The clocks change in the UK to observe British Summer Time (BST) in spring and return to Greenwich Mean Time (GMT) in autumn.

• Spring change (forward): Clocks go forward by one hour on the last Sunday in March, marking the start of BST. This gives longer evenings with more daylight after work and is the result of the historical movement to save daylight during summer.
• Autumn change (back): Clocks go back by one hour on the last Sunday in October, returning to GMT for the winter.

Context and purpose:

• The practice began in the early 20th century to make better use of daylight during the longer days of summer, reducing the need for artificial lighting and potentially saving energy.
• The concept was popularized by William Willett and was later established by law, with BST officially observed in many years since then, though the exact dates can vary around Easter in some years.

Key memory aid:

• “Spring forward, fall back” helps remember the direction of the change: spring = lose an hour, autumn = gain an hour.