Does the time difference between Bangalore and Singapore change during the year?

No. The gap stays at 2h 30m all year.

When is the best time to call Singapore from Bangalore?

Between 09:00 and 14:30 in Bangalore, which is 11:30 to 17:00 in Singapore.

Bangalore is 2h 30m behind Singapore. This gap is the same all year — neither city shifts its clocks relative to the other.

Bangalore

India

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Singapore

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A 9-to-5 day in each city overlaps for 5h 30m. That is 09:00–14:30 in Bangalore, which is 11:30–17:00 in Singapore.

City	Time zone	UTC offset
Bangalore · India	Asia/Kolkata	UTC+5:30
Singapore · Singapore	Asia/Singapore	UTC+8

What is the time difference between Bangalore and Singapore?: Bangalore is 2h 30m behind Singapore. This gap is the same all year — neither city shifts its clocks relative to the other.
Does the time difference between Bangalore and Singapore change during the year?: No. The gap stays at 2h 30m all year.
When is the best time to call Singapore from Bangalore?: Between 09:00 and 14:30 in Bangalore, which is 11:30 to 17:00 in Singapore.