Hi Akhil,
ISO 8601 uses the 24-hour clock system. The basic format is [mm][ss] and the extended format is :[mm]:[ss].
refers to a zero-padded hour between 00 and 24 (where 24 is only used to notate midnight at the end of a calendar day).
refers to a minute between 00 and 59.
refers to a second between 00 and 60 (where 60 is only used to notate an added leap second).
So a time might appear as either "134730" in the basic format or "13:47:30" in the extended format.
It is also acceptable to omit lower order time elements for reduced accuracy: :[mm], [mm] and are all used.
Midnight is a special case and can be referred to as both "00:00" and "24:00". The notation "00:00" is used at the beginning of a calendar day and is the more frequently used. At the end of a day use "24:00". Note that "2007-04-05T24:00" is the same instant as "2007-04-06T00:00" (see Combined date and time representations below).
There are no time zone designators in ISO 8601. Time is only represented as local time or in relation to UTC.
If no UTC relation information is given with a time representation, the time is assumed to be in local time. While it may be safe to assume local time when communicating in the same time zone, it is ambiguous when used in communicating across different time zones. It is usually preferable to indicate a time zone (zone designator) using the standardu2019s notation.
If the time is in UTC, add a 'Z' directly after the time without a space. 'Z' is the zone designator for the zero UTC offset. "09:30 UTC" is therefore represented as "09:30Z" or "0930Z". "14:45:15 UTC" would be "14:45:15Z" or "144515Z".
The offset from UTC is given in the format ±[hh]:[mm], ±[hh][mm], or ±[hh]. So if the time being described is one hour ahead of UTC (such as the time in Berlin during the winter), the zone designator would be "01:00", "0100", or simply "+01". This is appended to the time in the same way that 'Z' was above. The offset from UTC changes with daylight saving time, e.g. a time offset in Chicago, would be "-06:00" for the winter (Central Standard Time) and "-05:00" for the summer (Central Daylight Time).
The following times all refer to the same moment: "18:30Z", "22:30+04", "1130-0700", and "15:00-03:30". Nautical time zone letters are not used with the exception of Z. To calculate UTC time one has to subtract the offset from the local time, e.g. for "15:00-03:30" do 15:00 u2212 (u221203:30) to get 18:30 UTC.
The offset can also be used in the case where the UTC time is known, but the local offset is not. In this case the offset is "-00:00", which is semantically different from "Z" or "+00:00", as these imply that UTC is the preferred reference point for those times.
Regards,
Amith
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.