BST is British Summer Time — the clock the UK uses in the warmer months. In spring, British clocks jump forward one hour; in autumn they jump back. In summer, London is one hour ahead of Greenwich Mean Time (GMT), so 12:00 GMT is 13:00 BST. The point is to give people more daylight in the evening. Taiwan does not change its clocks now, so the time gap with Britain is not the same all year: it shrinks in British summer and grows again in winter. BST is only the UK's summer clock. Other countries do a similar trick under other names (in the US, daylight saving time). In winter, Britain is back on GMT, not BST.