What is the time difference between London and Kolkata?

Kolkata is 4 hours 30 minutes ahead of London. 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 Kolkata from London?

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

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.

Does Kolkata observe daylight saving time?

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

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

It is 16:30 in Kolkata, 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 London and Kolkata use?

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

Convert London time to Kolkata time

Kolkata is 4 hours 30 minutes ahead of London right now, so midday in London lands in the afternoon in Kolkata.

Convert a time

From

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 London, across for Kolkata.

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

Daylight saving time

Kolkata keeps one offset all year while London moves twice. That is the whole reason this difference is seasonal.

London

Observes daylight saving time

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

Kolkata

Does not observe daylight saving time

Standard: UTC+5:30

When you can actually talk

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

London 09:00–13:30Kolkata 13:30–18:00

Reference

The underlying data, in case you need to put it in a calendar invitation or a configuration file.

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

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

Common questions

What is the time difference between London and Kolkata?: Kolkata is 4 hours 30 minutes ahead of London. 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 Kolkata from London?: Between 09:00–13:30 in London, which is 13:30–18:00 in Kolkata. That is the only stretch where both cities are inside a 09:00–18:00 day.
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.
Does Kolkata observe daylight saving time?: No. Kolkata stays on UTC+5:30 all year, so its clocks never move.
If it is midday in London, what time is it in Kolkata?: It is 16:30 in Kolkata, 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 London and Kolkata use?: London uses Europe/London, currently UTC+1 (BST), and Kolkata uses Asia/Kolkata, currently UTC+5:30 (IST). Those identifiers are the ones to use in code — abbreviations are ambiguous and offsets change.