Minute counts

SIR – RA Collins (Letters, April 14) was wrong to state that clock time and sun time would be in harmony on April 15.

At midday, sun time is by definition the time when the sun is at its highest elevation. However, on April 15 clock time is set to British Summer Time, so the sun does not reach its zenith on the Greenwich meridian until one o’clock.

Moreover, we keep the same clock time across the United Kingdom, whereas sun time varies with longitude. The difference in sun time between Lowestoft in East Anglia and Barra in the Outer Hebrides, for example, is about 35 minutes, which far outweighs the minor fluctuations in sun time at a specific point due to the shape of the Earth’s orbit.

Dr PD Hills Norley, Cheshire