I have timezones in the following array format:
'America/New_York' => '(GMT-05:00) Eastern Time (US & Canada)',
'Europe/Lisbon' => '(GMT) Greenwich Mean Time : Lisbon',
etc.
How do I go about displaying a user-friendly summer/daylight savings time dependent timezone identifier to the user?
For example, displaying the time now in New York would append "(EDT)" to the time, which would make sense for local users. I want to avoid having to display ((GMT-05:00) Eastern Time (US & Canada)) or just (GMT-05:00), which isn't strictly accurate all year round.
Ideally then, is there a web service/database that can take a tz string in the format "America/New_York", and a timestamp as paramters and return the abbreviation in the formats here?
strftime's %Z format specifier gives you this abbreviation. You didn't say what programming language you are using, but most programming languages give you access to strftime in one way or another.
Python:
import pytz
from datetime import datetime
here = pytz.timezone('Asia/Tokyo')
print here.localize(datetime.utcnow()).strftime("%Z")
there = pytz.timezone('America/Montreal')
print there.localize(datetime.utcnow()).strftime("%Z")
PHP:
date_default_timezone_set("Asia/Tokyo");
echo strftime("%Z");
date_default_timezone_set("America/Montreal");
echo strftime("%Z");
Related
For example my local time_zone is Canada and i am getting date in Chennai timezone. How can I convert the Chennai timezone to UTC?
Using server time
You can call ActiveSupport::TimeWithZone#utc on the result.
Example:
Time.zone.now.utc
Keep in mind that .now is using the server time zone when config.time_zone is set.
When you receive a time
If you are getting the datetime in Chennai timezone it will probably look like this: 2019-11-26T12:20:00.655+05:30
To convert it in different time zone, use:
time = Time.parse("2019-11-26T12:20:00.655+05:30")
pacific_time = time.in_time_zone("Pacific Time (US & Canada)")
# and then UTC if you want
pacific_time.utc
Rails 5.2.3
I have a date:
"Apr-03-2013 17:47:00"
I have a date zone:
"America/Los_Angeles"
I am trying to turn it into a string:
"Apr-03-2013 17:47:00 Pacific Daylight Time (GMT-07)"
The best I can come up with is:
time_obj = ActiveSupport::TimeZone["America/Los_Angeles"].parse("2013-04-03 17:47:00")
Time.at(time_obj).strftime("%b-%d-%Y %H:%M:%S %Z")
Which gives me:
"Apr-03-2013 17:47:00 PDT"
Any ideas?
I believe you need custom logic and/or you own database of timezones to get it exactly like that.
Using %Z with strftime is going to give you what ever your OS likes and there are a few disclaimers in the ruby docs.
One idea that you might get some mileage out of: If you are starting with a time zone identifier like "America/Los_Angeles" then you can use ActiveSupport::TimeZone::MAPPING to get a friendlier name, or at least a Rails time zone name.
eg:
ActiveSupport::TimeZone::MAPPING.key("America/Los_Angeles")
=> "Pacific Time (US & Canada)"
But that won't work for every identifier:
ActiveSupport::TimeZone::MAPPING.key("America/Detroit")
=> nil
You can see which ones will map like this:
TZInfo::Country.get('US').zone_identifiers.map {|ident| [ident, ActiveSupport::TimeZone::MAPPING.key(ident)] }
So in that case you need to fall back to the identifier you have, or perhaps this approach might work.
Then you'd need to deal with the daylight savings part, here you can use dst?
ActiveSupport::TimeZone["America/Los_Angeles"].parse("2013-04-03 17:47:00").dst?
Then you'd need to splice all that together! ... and add the offset as well.
I'm importing an object from an API with a datetime that looks like this:
"2017-06-28 09:00:00"
This time is in the user's time zone, which is known in my application. (i.e. Pacific Time (US & Canada))
Datetimes are stored in my database as datetime format in UTC. When we display dates on the front-end, we account for the user's time zone (ie datetime.in_time_zone(user_time_zone)).
How do I save the datetime in my database correctly?
You should be able to append your apps timezone to the end of the datetime string.
time = "2017-06-28 09:00:00"
time += Time.zone.name
Parsing that will give you the time in Pacific Time (US & Canada). Or use ActiveSupport.
time_pacific = DateTime.parse(time)
### ActiveSupport version ###
time_pacific = ActiveSupport::TimeZone.new(Time.zone.name).parse("2017-06-28 09:00:00")
You can then call #utc on that to get the correct UTC time from your original string.
time_utc = time_pacific.utc
I'm using Rails 3.2 and ruby 1.9.3 on Debian. I have an app that collects a date, time, and timezone in the form of strings via an HTML form. Something like this:
start_date: "04-15-2010",
start_time: "10:00:00",
timezone: "Central Time (US & Canada)"
What I'd like to do is parse these 3 elements into a single date that is saved into my database as UTC, which in this case would add 7 hours to the start time, once it's in the UTC time zone.
So the stored time would be 17:00 once it's in the DB as UTC instead of the received Central time.
I have tried something like this to parse the date:
ActiveSupport::TimeZone[timezone].at DateTime.strptime("{ 2012-04-09 20:00:00 }", "{ %Y-%m-%d %H:%M:%S }").to_i
However, I'm not able to incorporate the time zone into the resulting time with %Z. It either doesn't parse or the time is interpreted as UTC not Central time. So my question is, how to coerce a date string into a certain time zone without changing the value of the actual date/time stored. I'd like to be able to parse the string into a date/time object that includes the correct time zone with it at that time so that future time zone conversions are accurate. I've looked all over and can't find a way to do this. It's strange, since this seems like something common one does with dates inputted from HTML forms. Thank you for any help.
Try this:
zone = "Central Time (US & Canada)"
ActiveSupport::TimeZone[zone].parse("2013-04-03 17:47:00")
Use String#in_time_zone (Rails 4+)
I personally prefer using String#in_time_zone:
>> '22.09.1986 10:30'.in_time_zone('Central Time (US & Canada)')
# => Mon, 22 Sep 1986 10:30:00 CDT -05:00
This parses the date and time in the String into the time zone provided.
%Z is the correct way to specify a Time zone name. Have you tried the following ?
date_and_time = '%m-%d-%Y %H:%M:%S %Z'
DateTime.strptime("04-15-2010 10:00:00 Central Time (US & Canada)",date_and_time)
This is the method that I came up with. Not the prettiest, but it works. Allows parsing the string using a specified format, and then turning it into the format that I know Time.zone.parse requires.
class ActiveSupport::TimeZone
def strptime(time, format='%m/%d/%Y')
formatted = Time.strptime(time, format).strftime('%Y-%m-%d %T')
parse(formatted)
end
end
Then you can do something like what was mentioned in another question, but with a specified format:
zone = "Central Time (US & Canada)"
ActiveSupport::TimeZone[zone].strptime('2013-04-03', '%Y-%m-%d')
Or if you already have a time zone set:
Time.zone = "Central Time (US & Canada)"
Time.zone.strptime('01/13/2006')
I used a default format of %m/%d/%Y because that's what my user input is most of the time. You can customize this to your needs, or use the default format DateTime uses which is believe is iso8601 (%FT%T%z)
I've finally found the dirty, yet definitive way to do this.
First, parse the string using plain Ruby Time.strptime like this:
time = Time.strptime('12 : 00 : PM', '%I : %M : %p')
This way you get the parsed Time, but not yet in correct timezone. To fix that, let's convert the time to string form and parse it with the standard ActiveSupport::TimeZone#parse
Time.zone.parse(time.to_s)
The result is the ActiveSupport::TimeWithZone with our time parsed into the correct timezone.
The reason why we have to do it this way is that neither ActiveSupport::TimeZone nor ActiveSupport::TimeWithZone support the strptime method. So we have to parse the Time with core Ruby strptime that does not have timezone information, convert it to format acceptable in ActiveSupport objects and then parse it yet again.
To have DateTime take the date string and attach a timezone other than UTC without changing the values of the date string , use this, its easy , doesnt break on leap day :)
xx = DateTime.strptime("9/1/15 #{object.time_zone}", "%m/%d/%Y %Z")
Convert specific date format in UTC.
ActiveSupport::TimeZone['UTC'].parse(Time.strptime('01/24/2019T16:10:16', "%m/%d/%YT%H:%M:%S").asctime)
I am looking for some help in how I can store the correct timezone in Rails, from data that provides me with a UTC offset, and DST.
The data comes from http://openflights.org/data.html
Timezone Hours offset from UTC. Fractional hours are expressed as decimals, eg. India is 5.5.
DST Daylight savings time. One of E (Europe), A (US/Canada), S (South America), O (Australia), Z (New Zealand), N (None) or U (Unknown).
I am wondering how I could use this data in Rails to store the timezone of these airports as a string in a Timezone column that Rails would recognise.
I don't think there there is a solution for this, unless you create a custom mapping of the DST and offset to a particular timezone.
I ended up using the geonames.org webservice, to find out the timezone based on latitude/longitude.
I needed the same functionality in the slightly simpler case of a database of USA zipcodes which includes a UTC hours offset and Y/N field indicating if it participates in daylight savings time, so West coast USA zipcodes in this database all have "-8" and "Y".
I could not find a built-in Rails method to do it, so I manually created a lookup hash where the key is the UTC & DST fields catenated, eg, "#{utc}#{dst}" and the value is the timezone name. This method could work for utc offsets such as "5.5" as well.
In the method that does the lookup is given the utc and dst values, I specify a default timezone (USA west coast for example) in the case where the hash lookup returns nil because an unexpected value such as "-5N" (since the east coast does not have any non-DST states that should never occur).
But the same method could be applied globally by creating a hash that represented all the possible timezone with both Y and N values for daylight savings time.
class MyZip
HOUR_DST_TO_TIMEZONE_NAME = {
"-5Y" => "Eastern Time (US & Canada)",
"-6Y" => "Central Time (US & Canada)",
"-7Y" => "Mountain Time (US & Canada)",
"-7N" => "Arizona",
"-8Y" => "Pacific Time (US & Canada)",
"-9Y" => "Alaska",
"-10N" => "Hawaii"
}
def self.timezone_name_from_zip_hour_dst(utc, dst)
key = "#{utc}#{dst}"
return HOUR_DST_TO_TIMEZONE_NAME[key] || MyZip.unknown_timezone_name
end
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