If using FAT32, remember that timestamps are stored in local time, not UTC. Regardless of the previous bullet point, server-side code, including web sites, should never expect the local time zone of the server to be anything in particular. On servers, set hardware clocks and OS clocks to UTC rather than a local time zone. Keep your OS, database and application tzdata files in sync, between themselves and the rest of the world. Be aware of items like this in any calculations that involve multiple zones.Ĭonsider the type of time (actual event time, broadcast time, relative time, historical time, recurring time) what elements (timestamp, time zone offset and time zone name) you need to store for correct retrieval - see "Types of Time" in answer. This now means that for 48 weeks of the year the difference between London time and New York time is 5 hours and for 4 weeks (3 in the spring, 1 in the autumn) it is 4 hours. However, in 2007 the US changed the dates that the clocks get changed on. For instance, historically US and UK used the same dates to 'spring forward' and 'fall back'. Remember that time zones and offsets are not fixed and may change. Therefore, plan to convert UTC timestamps to a local time zone before applying application logic. Most business rules use civil time, rather than UTC or GMT. (Also, the file has fallen out of maintenance.) While its API claims to support standard IANA (aka "zoneinfo") identifiers, it crudely maps them to fixed offsets without considering the rich history of changes each zone may have had. These include cctz, ICU, and Howard Hinnant's "tz" library.ĭo not use Boost for time zone conversions. If using C++, be sure to use a library that uses the properly implements the IANA timezone database. To keep PHP with up to date Olson data, install periodically the timezonedb PECL package see answer. Be careful when using.ĭateTimeZone::listAbbreviations() - see answer. If using PHP > 5.2, use the native time zones conversions provided by DateTime, and DateTimeZone classes. If using JavaScript, use moment.js with the moment-timezone extension. NET without Noda Time, consider that DateTimeOffset is often a better choice than DateTime. If using Java, use java.time for Java 8, or use Joda Time for Java 7 or lower. Remember that time zone offsets are not always an integer number of hours (for example, Indian Standard Time is UTC+05:30, and Nepal uses UTC+05:45). When scheduling future events, usually local time is preferred instead of UTC, as it is common for the offset to change. If you might later need to modify the timestamp, include the original time zone ID so you can determine if the offset may have changed from the original value recorded. This value should always be based on UTC, without any time zone adjustment. If you require higher precision, use milliseconds instead. When storing timestamps as a numeric value, use Unix time - which is the number of whole seconds since (excluding leap seconds). Often this is done with two separate fields, but some platforms support a datetimeoffset type that can store both in a single field. In some cases, you may need to store both the UTC time and the equivalent local time. If instead you choose to persist a time using a local time value, include the local time offset from UTC, such that the timestamp can later be interpreted unambiguously. Notice that UTC is also known as Zulu or Z time.) (GMT and UTC are equivalent with this regard, but it is preferred to use the term UTC. Whenever you are referring to an exact moment in time, persist the time according to a unified standard that is not affected by daylight savings.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |