![]() When instantiated without parameters, the date object holds the current date and time ( new Date() holds the current date). However, by default, when we output the date and time, the Date object converts the output to the local time zone, the time zone of the environment where the JavaScript code is running (e.g., a browser, Node.js, etc.) The Date object holds the current date and time in UTC internally. In JavaScript we use the Date object to work with date and time: const date = new Date ( ) The difference is that the Unix timestamp is the number of seconds since the Unix epoch while in JavaScript it is the number of milliseconds. This number looks similar to the Unix timestamp. The Date objectįundamentally, a JavaScript date is specified as the number of milliseconds from the 1 January 1970 00:00:00 UTC. Learn more about the Unix timestamp on Wikipedia: Unix time. The Unix timestamp is one of the common formats for storing date and time in operating systems and databases. ![]() Positive integers represent the dates after the Unix epoch, while negative integers represent the dates before the Unix epoch. Unix timestampĪ common format to represent date and time values in computer programming is the Unix timestamp, which is a number of seconds between the Unix epoch (1 January 1970 00:00:00 UTC) and another date (e.g., 1620758838). Operating systems and other computer software use these databases for time zone processing and conversions. ![]() The most popular one is IANA - Time Zone Database, also known as tz or zoneinfo. Therefore, there is a number of databases where the information about the time zone changes is tracked. The date and time DST starts and ends depends on a country or a political unit (e.g., European Union.)Īlso, a political region's time zone offset and/or the date and time when the DST starts and ends could have been changed at some point in history. For example, in Ukraine we turn the clock forward one hour on the last Sunday of March at 03:00 and we return back to the standard time (turning the clock backward one hour) in the last Sunday of October at 04:00. This is the practice of turning the clock forward one hour from standard time during the warmer months in order to get more daylight during the hours we're usually awake. The geographical reference point for UTC is the prime meridian (longitude = 0°), that runs through the Royal Observatory in Greenwich, London, United Kingdom.Īdditionally, in various regions of the world people practice Daylight Saving Time (DST) or in other words - summer time. A country can choose a UTC offset that differs from that country's actual georgraphical location's UTC offset.Īll time zones are defined as offsets to Coordinated Universal Time (UTC), ranging from UTC-12:00 to UTC+14:00. Also, it's important to mention that the time zone choice/definition in a particular country/region may be affected by a political decision. For example, in the summer, while in Kyiv the time is 21:00, in New York the time is 14:00 (minus seven hours). Time zonesĭepending on the geographical area or a political unit (e.g., a country), the time zone can differ. In Ukraine, the date is usually written in the format "DD-MM-YYYY" (the day is first), while in the United States the common format is "MM-DD-YYYY" (the month is first). Date formatsĭate and time can be represented in many different formats. Therefore, it's important to understand various nuances around working with date and time. And, generally in the software we build we capture and process the date and time of various data records and events. Computer software is used by people from anywhere in the world and the time in one region can differ from the time in another region. ![]() Therefore, as developers we get to work with date and time quite frequently. Time plays an essential role in our lives. Calculating the difference between dates.
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