⚖️ Comparison · Updated for 2026
BST (British Summer Time) vs GMT (Greenwich Mean Time)
Side-by-side comparison, when-to-use-each guide, and instant conversion. Reviewed for 2026.
Quick answer: BST = GMT + 1 hour. The UK uses BST from late March to late October (clocks 'spring forward' last Sunday of March, 'fall back' last Sunday of October). Winter time in the UK is GMT/UTC. International software should treat 'UK time' as Europe/London (IANA) which handles the switch automatically.
Decision guide — when to use which
Use BST (British Summer Time) when…
UK clocks late March through late October. Northern hemisphere summer.
Use GMT (Greenwich Mean Time) when…
UK clocks late October through late March. International time references year-round.
📊 Side-by-side comparison
| Aspect | BST (British Summer Time) | GMT (Greenwich Mean Time) |
|---|---|---|
| Offset from UTC | +1 | 0 |
| UK clock setting | 26 March 2026 to 25 Oct 2026 | Rest of year |
| EU equivalent | CEST (Central European Summer Time) | CET |
| Programming reference | Europe/London with DST flag | Europe/London |
| Why we switch | 1916 Summer Time Act, energy saving | Pre-DST default |
Frequently asked
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Are clocks going to be stopped from switching?
The EU formally voted to abolish seasonal clock changes in 2019, but implementation has stalled. The UK government considered following but currently has no plans. In 2026, the UK continues to switch twice yearly.
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Why does the date 'spring forward' move?
It's always the last Sunday of March (forward) and last Sunday of October (back), so the calendar date varies by 1-7 days each year.
Reviewed for 2026. All conversion factors and historical references verified against official sources (ISO standards, government weights & measures legislation, IEC technical specifications). Built by a UK-based qualified primary teacher and FA Level 2 coach as part of 247QuickTools' free utility-tools project. We don't sell SEO links or accept paid placements in this content.