TL;DR: You should always store datetimes in UTC and convert to proper timezone on display.<\/p>\n
A timezone offset refers to how many hours the timezone is from Coordinated Universal Time (UTC). The offset of UTC is The local time minus the offset of its timezone is UTC time. For instance, ref: \u5230\u5e95\u662f GMT+8 \u9084\u662f UTC+8\uff1f ref: ref: Any naive A naive ref: A aware There are two useful methods: You should avoid For working with ref: Naive and aware ref: ref: We might receive a Unix timestamp from a JavaScript client.<\/p>\n ref: ref: ref: You should always store datetimes in UTC and convert to proper timezone on display.<\/p>\n","protected":false},"author":1,"featured_media":501,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[50,2],"class_list":["post-500","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-about-python","tag-datetime","tag-python"],"_links":{"self":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts\/500","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/comments?post=500"}],"version-history":[{"count":0,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/posts\/500\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/media\/501"}],"wp:attachment":[{"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/media?parent=500"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/categories?post=500"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vinta.ws\/code\/wp-json\/wp\/v2\/tags?post=500"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}+00:00<\/code>, and the offset of Asia\/Taipei<\/code> timezone is UTC+08:00<\/code> (you could also present it as GMT+08:00<\/code>). Basically, there is no perceptible difference between Greenwich Mean Time (GMT) and UTC.<\/p>\n18:00+08:00<\/code> of Asia\/Taipei<\/code> minuses timezone offset +08:00<\/code> is 10:00+00:00<\/code>, 10 o'clock of UTC. On the other hand, UTC time plus local timezone offset is local time.<\/p>\n
\nhttps:\/\/opensource.com\/article\/17\/5\/understanding-datetime-python-primer<\/a>
\nhttps:\/\/julien.danjou.info\/blog\/2015\/python-and-timezones<\/a><\/p>\n
\nhttp:\/\/pansci.asia\/archives\/84978<\/a><\/p>\nInstallation<\/h2>\n
$ pip install -U python-dateutil pytz tzlocal<\/code><\/pre>\nShow System Timezone<\/h2>\n
import tzlocal\n\ntzlocal.get_localzone()\n# <DstTzInfo 'Asia\/Taipei' LMT+8:06:00 STD>\n\ntzlocal.get_localzone().zone\n# 'Asia\/Taipei'\n\nfrom time import gmtime, strftime\nprint(strftime(\"%z\", gmtime()))\n# +0800<\/code><\/pre>\n
\nhttps:\/\/github.com\/regebro\/tzlocal<\/a>
\nhttps:\/\/stackoverflow.com\/questions\/13218506\/how-to-get-system-timezone-setting-and-pass-it-to-pytz-timezone\/<\/a><\/p>\nFind Timezones Of A Certain Country<\/h2>\n
import pytz\n\npytz.country_timezones('tw')\n# ['Asia\/Taipei']\n\npytz.country_timezones('cn')\n# ['Asia\/Shanghai', 'Asia\/Urumqi']<\/code><\/pre>\n
\nhttps:\/\/pythonhosted.org\/pytz\/#country-information<\/a><\/p>\nOffset-naive Datetime<\/h2>\n
datetime<\/code> would be present as local timezone but without tzinfo<\/code>, so it is buggy.<\/p>\ndatetime<\/code> object contains no timezone information. The datetime_obj.tzinfo<\/code> will be set to None<\/code> if the object is naive. Actually, datetime<\/code> objects without timezone should be considered as a "bug" in your application. It is up for the programmer to keep track of which timezone users are working in.<\/p>\nimport datetime\n\nimport dateutil.parser\n\ndatetime.datetime.now()\n# return the current date and time in local timezone, in this example: Asia\/Taipei (UTC+08:00)\n# datetime.datetime(2018, 2, 2, 9, 15, 6, 211358)), naive\n\ndatetime.datetime.utcnow()\n# return the current date and time in UTC\n# datetime.datetime(2018, 2, 2, 1, 15, 6, 211358), naive\n\ndateutil.parser.parse('2018-02-04T16:30:00')\n# datetime.datetime(2018, 2, 4, 16, 30), naive<\/code><\/pre>\n
\nhttps:\/\/docs.python.org\/3\/library\/datetime.html<\/a>
\nhttps:\/\/dateutil.readthedocs.io\/en\/stable\/<\/a><\/p>\nOffset-aware Datetime<\/h2>\n
datetime<\/code> object embeds a timezone information. Rules of thumb for timezone in Python:<\/p>\n\n
datetime<\/code> objects.<\/li>\npytz.utc.localize(naive_dt)<\/code> for converting naive datetime<\/code> to timezone be offset-aware, and aware_dt.astimezone(pytz.timezone('Asia\/Taipei'))<\/code> for adjusting timezones of offset-aware objects.<\/p>\nnaive_dt.astimezone(some_tzinfo)<\/code> which would be converted to aware datetime as system timezone then convert to some_tzinfo<\/code> timezone.<\/p>\nimport datetime\n\nimport pytz\n\nnow_utc = pytz.utc.localize(datetime.datetime.utcnow())\n# equals to datetime.datetime.now(pytz.utc)\n# equals to datetime.datetime.utcnow().replace(tzinfo=datetime.timezone.utc)\n# datetime.datetime(2018, 2, 4, 10, 17, 40, 679562, tzinfo=<UTC>), aware\n\nnow_taipei = now_utc.astimezone(pytz.timezone('Asia\/Taipei'))\n# convert to another timezone\n# datetime.datetime(2018, 2, 4, 18, 17, 40, 679562, tzinfo=<DstTzInfo 'Asia\/Taipei' CST+8:00:00 STD>), aware\n\nnow_utc.isoformat()\n# '2018-02-04T10:17:40.679562+00:00'\n\nnow_taipei.isoformat()\n# '2018-02-04T18:17:40.679562+08:00'\n\nnow_utc == now_taipei\n# True<\/code><\/pre>\npytz<\/code>, it is recommended to call tz.localize(naive_dt)<\/code> instead of naive_dt.replace(tzinfo=tz)<\/code>. dt.replace(tzinfo=tz)<\/code> does not handle daylight savings time correctly. <\/p>\ndt1 = datetime.datetime.now(pytz.timezone('Asia\/Taipei'))\n# datetime.datetime(2018, 2, 4, 18, 22, 28, 409332, tzinfo=<DstTzInfo 'Asia\/Taipei' CST+8:00:00 STD>), aware\n\ndt2 = datetime.datetime(2018, 2, 4, 18, 22, 28, 409332, tzinfo=pytz.timezone('Asia\/Taipei'))\n# datetime.datetime(2018, 2, 4, 18, 22, 28, 409332, tzinfo=<DstTzInfo 'Asia\/Taipei' LMT+8:06:00 STD>), aware\n\ndt1 == dt2\n# False<\/code><\/pre>\n
\nhttps:\/\/pythonhosted.org\/pytz\/<\/a><\/p>\ndatetime<\/code> objects are not comparable.<\/p>\nnaive = datetime.datetime.utcnow()\naware = pytz.utc.localize(naive)\n\nnaive == aware\n# False\n\nnaive >= aware\n# TypeError: can't compare offset-naive and offset-aware datetimes<\/code><\/pre>\nParse String to Datetime<\/h3>\n
python-dateutil<\/code> usually comes in handy.<\/p>\nimport dateutil.parser\nimport dateutil.tz\n\ndt1 = dateutil.parser.parse('2018-02-04T19:30:00+08:00')\n# datetime.datetime(2018, 2, 4, 19, 30, tzinfo=tzoffset(None, 28800)), aware\n\ndt2 = dateutil.parser.parse('2018-02-04T11:30:00+00:00')\n# datetime.datetime(2018, 2, 4, 11, 30, tzinfo=tzutc()), aware\n\ndt3 = dateutil.parser.parse('2018-02-04T11:30:00Z')\n# datetime.datetime(2018, 2, 4, 11, 30, tzinfo=tzutc()), aware\n\ndt1 == dt2 == dt3\n# True<\/code><\/pre>\n
\nhttps:\/\/dateutil.readthedocs.io\/en\/stable\/<\/a><\/p>\nConvert Datetime To Unix Timestamp<\/h2>\n
import datetime\n\nnaive_dt = datetime.datetime(2018, 9, 10, 0, 0, 0)\nnaive_timestamp = aware_dt.timestamp()\n# naive_dt would be in local timezone, in this example: Asia\/Taipei (UTC+08:00)\n\naware_dt = datetime.datetime(2018, 9, 10, 0, 0, 0, tzinfo=datetime.timezone(datetime.timedelta(hours=8)))\naware_timestamp = aware_dt.timestamp()\n\nnaive_timestamp == aware_timestamp\n# True\n\n# MongoDB stores all datetimes in UTC timezone\ndt_fetched_from_mongodb.replace(tzinfo=datetime.timezone.utc).timestamp()<\/code><\/pre>\nParse Unix Timestamp To Datetime<\/h2>\n
import datetime\nimport time\n\nimport pytz\n\nts = time.time()\n# seconds since the Epoch (1970-01-01T00:00:00 in UTC)\n# 1517748706.063205\n\ndt1 = datetime.datetime.fromtimestamp(ts)\n# return the date and time of the timestamp in local timezone, in this example: Asia\/Taipei (UTC+08:00)\n# datetime.datetime(2018, 2, 4, 20, 51, 46, 63205), naive\n\ndt2 = datetime.datetime.utcfromtimestamp(ts)\n# return the date and time of the timestamp in UTC timezone\n# datetime.datetime(2018, 2, 4, 12, 51, 46, 63205), naive\n\npytz.timezone('Asia\/Taipei').localize(dt1) == pytz.utc.localize(dt2)\n# True<\/code><\/pre>\n
\nhttps:\/\/stackoverflow.com\/questions\/13890935\/does-pythons-time-time-return-the-local-or-utc-timestamp<\/a><\/p>\nvar moment = require('moment')\nvar ts = moment('2018-02-02').unix()\n\/\/ 1517500800<\/code><\/pre>\n
\nhttps:\/\/momentjs.com\/docs\/#\/parsing\/unix-timestamp\/<\/a><\/p>\nStore Datetime In Databases<\/h2>\n
\n
\nhttps:\/\/tommikaikkonen.github.io\/timezones\/<\/a>
\nhttps:\/\/blog.elsdoerfer.name\/2008\/03\/03\/fun-with-timezones-in-django-mysql\/<\/a><\/p>\nTools<\/h2>\n
\nhttps:\/\/www.epochconverter.com\/<\/a>
\nhttps:\/\/www.timeanddate.com\/worldclock\/converter.html<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"