Daylight Saving Time (DST)

UTC does not change with a change of seasons. The Local time may change for political or economic reasons due to daylight. See Daylight Savings Time (or DST)

Time Zone

Time zones in UTC are longitudinal time zones that are expressed in UTC using positive or negative offsets from the origin, known as UTC or Z.

Z is a reference to:

• the Z of zero hour (The offset is 0),
• the nautical time zone (GMT) notation, which has been denoted by a Z since about 1950.

Because in the phonetic alphabet (Military) (ie Tango, Charlie, Bravo) , the Z is known as Zulu , UTC is also known as the Zulu time .

The time zone is therefore denoted:

• UTC±HH:MM
• or Z±HH:MM

where ±HH:MM is an offset which ranges from

• UTC−12:00 in the west
• to UTC+14:00 in the east

For example in the ISO string, the time zones are denoted with a Z

2023-09-01T10:39:08.582Z

Javascript

Demo of the UTC ISO string

// Now
const now = new Date(); 

// To Iso string at UTC 0
console.log('The time in the UTC+0 timezone is '+now.toISOString());

// Time to your local
console.log('Your local time is '+now.toLocaleString());

• Result: The timezone offset in the ISO string is zero as denoted by the suffix Z

Java

see What is a Java Instant? (Moment)

new Date().toInstant()

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