Ruby: convert "US/Eastern" time zone names to "Central Time (US & Canada)" - ruby-on-rails

I've got an old database with time zone formats like:
US/Eastern
Australia/Melbourne
In my new Rails app, I'm saving them as:
Eastern Time (US & Canada)
Melbourne
How can I convert the old to the new? I've been messing around with ActiveSupport::TimeZone, but can't figure out the right combination to get from one to the other.
I was hoping I could create a new object, then return the newly formatted name, but it just returns the name I gave it. Example:
> tz = ActiveSupport::TimeZone.new("US/Eastern")
=> (GMT-05:00) US/Eastern
> tz.name
=> "US/Eastern"
Thanks in advance!

This is pretty ugly, but it's the only way I've found to do it:
city = TZInfo::Timezone.get('US/Eastern').instance_eval('#linked_timezone').name
ActiveSupport::TimeZone::MAPPING.invert[city]
Edit:
For this code to work with either city or zone, you can do this:
zone = TZInfo::Timezone.get(zone_name)
city = (zone.instance_eval('#linked_timezone') || zone).name
ActiveSupport::TimeZone::MAPPING.invert[city]

Related

Converting a date string into a time zone specific format

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.

Parsing a TimeZone name string that includes GMT offset hours

I did find this question but I am still stumbling around looking for a simple solution to the following:
An API call returns the following format which looks like they are using Time.zone.to_s
irb> ShopifyAPI::Shop.current.timezone
=> "(GMT-08:00) Pacific Time (US & Canada)"
I would like to parse the "(GMT-08:00) Pacific Time (US & Canada)" into a Ruby class and output the TimeZone name "Pacific Time (US & Canada)"
Alternately I could just strip the "(GMT-08:00)" offset and be left with a clean TimeZone name "Pacific Time (US & Canada)" but this seems like a messy string editing solution.
ShopifyAPI::Shop.current returns properties documented here. Yes, timezone is one of them, but it is intended to be a display name, not something you should parse.
Instead, use the iana_timezone property, which will give you the IANA time zone identifier, such as America/Los_Angeles. These are compatible with Rails, as well as Ruby's tzinfo gem, and also are used in many other platforms.
irb> ShopifyAPI::Shop.current.timezone
=> "(GMT-08:00) Pacific Time (US & Canada)"
irb> ShopifyAPI::Shop.current.iana_timezone
=> "America/Los_Angeles"
If you want to get a Rails time zone from there, you can use the MAPPING constant defined in ActiveSupport::TimeZone. Though I'd avoid it if possible, for the reasons mentioned in the timezone tag wiki in the "Rails Time Zone Identifiers" section at the bottom.
If you are confident about the API and string format you are going to receive, you can manipulate string as
string.partition(')').last.strip
# => Pacific Time (US & Canada)

How to set custom time zone in Rails? "-03:30GMT"

I know we can set time zone with
Time.zone = "Eastern Time (US & Canada)"
But how to set with UTC/GMT time, I want to set time zone to -03:30GMT, but I cant find any place which lies in that time zone, so how to set it by giving values?
try this. this will work
Time.zone = -12600
this will give you the full list of timezones from the library
ActiveSupport::TimeZone.zones_map.values.collect { |z| z.tzinfo.name }.compact.uniq.each do |tz|
puts "#{ActiveSupport::TimeZone.seconds_to_utc_offset(Time.now.in_time_zone(tz).utc_offset)}\t#{tz}"
end; nil
I cant find any place which lies in that time zone
It looks like all zones are covered

Rails: Take an unformatted datetime and assign it a time zone w/o changing the time?

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

Rails: How to parse date-time string into a specific time zone

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)

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