What is the time difference between Kolkata and London?

London is 4 hours 30 minutes behind Kolkata. That figure is current — it changes by an hour when either city starts or ends daylight saving, and the exact dates are listed above.

When is the best time to call London from Kolkata?

Between 13:30–18:00 in Kolkata, which is 09:00–13:30 in London. That is the only stretch where both cities are inside a 09:00–18:00 day.

Does Kolkata observe daylight saving time?

No. Kolkata stays on UTC+5:30 all year, so its clocks never move.

Does London observe daylight saving time?

Yes. London runs on UTC+0 in winter and UTC+1 in summer. The next change is on 2026-10-25, when clocks go back by 60 minutes.

If it is midday in Kolkata, what time is it in London?

It is 07:30 in London, on the same calendar date. That holds for the current offsets; it shifts by an hour around the daylight saving dates listed above.

Which time zones do Kolkata and London use?

Kolkata uses Asia/Kolkata, currently UTC+5:30 (IST), and London uses Europe/London, currently UTC+1 (BST). Those identifiers are the ones to use in code — abbreviations are ambiguous and offsets change.

Convert Kolkata time to London time

Right now London runs 4 hours 30 minutes behind Kolkata. That gap is not fixed: it moves when either city changes its clocks.

Convert a time

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Date

Time

Converted time

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The converter needs JavaScript to run. Everything below — offsets, daylight saving dates and the hour-by-hour table — is part of the page and works without it.

Hour by hour

The whole day mapped across: read down the left for Kolkata, across for London.

Kolkata	London
00:00	19:30previous day
01:00	20:30previous day
02:00	21:30previous day
03:00	22:30previous day
04:00	23:30previous day
05:00	00:30
06:00	01:30
07:00	02:30
08:00	03:30
09:00	04:30
10:00	05:30
11:00	06:30
12:00	07:30
13:00	08:30
14:00	09:30
15:00	10:30
16:00	11:30
17:00	12:30
18:00	13:30
19:00	14:30
20:00	15:30
21:00	16:30
22:00	17:30
23:00	18:30

Daylight saving time

London changes its clocks; Kolkata does not. The difference between them therefore shifts by an hour twice a year.

Kolkata

Does not observe daylight saving time

Standard: UTC+5:30

London

Observes daylight saving time

Standard: UTC+0
Daylight: UTC+1
Next change: 2026-10-25 −60m

When you can actually talk

The window is 4 hours 30 minutes wide — 13:30–18:00 in Kolkata, 09:00–13:30 in London.

Kolkata 13:30–18:00London 09:00–13:30

Reference

The zone identifiers and offsets behind everything above.

	Kolkata	London
IANA zone	Asia/Kolkata	Europe/London
Abbreviation	IST	BST
Standard offset	UTC+5:30	UTC+0
Daylight offset	—	UTC+1
Clock changes this year	0	2
Country	India	United Kingdom

Example, not the current time. Live times appear once the page loads.

Common questions

What is the time difference between Kolkata and London?: London is 4 hours 30 minutes behind Kolkata. That figure is current — it changes by an hour when either city starts or ends daylight saving, and the exact dates are listed above.
When is the best time to call London from Kolkata?: Between 13:30–18:00 in Kolkata, which is 09:00–13:30 in London. That is the only stretch where both cities are inside a 09:00–18:00 day.
Does Kolkata observe daylight saving time?: No. Kolkata stays on UTC+5:30 all year, so its clocks never move.
Does London observe daylight saving time?: Yes. London runs on UTC+0 in winter and UTC+1 in summer. The next change is on 2026-10-25, when clocks go back by 60 minutes.
If it is midday in Kolkata, what time is it in London?: It is 07:30 in London, on the same calendar date. That holds for the current offsets; it shifts by an hour around the daylight saving dates listed above.
Which time zones do Kolkata and London use?: Kolkata uses Asia/Kolkata, currently UTC+5:30 (IST), and London uses Europe/London, currently UTC+1 (BST). Those identifiers are the ones to use in code — abbreviations are ambiguous and offsets change.