I have left my application.rb as it was and by default it is storing datetime in UTC.
Now at the UI level (for displaying only) I want to convert the datetime to the user specific timezone.
How can I convert the UTC datetime I get from postgresql and then convert it to the timezone that I will store for each user.
I want to make this conversion using the Offset so like: -5:00 or +4:00
Is it ok to do this, because I was just checking some locations and it seems their offset changes during the season.
E.g. virginia goes from UTC -5 to UTC -4 depending on the month.
http://www.timeanddate.com/time/zone/usa/richmond
If UTC is not consistant then I should just store the zone in the database for each user?
When I made an app with scheduling events, I had to add timezones to the User model to offset their scheduling.
When I recorded the offset, I used the following code:
<%= time_zone_select "user",
"timezone",
ActiveSupport::TimeZone.us_zones,
{default: "Mountain Time (US & Canada)"},
{class: "form-control"} %>
Because Rails has time zones built into their ActiveSupport model. You could use ActiveSupport::TimeZone.all if you wanted users to be global.
Here's some info on time_zone_select
Then depending on how you use it, you can just set
Time.zone = current_user.timezone unless current_user.nil?
or something similar in your application.rb file.
UPDATE
I personally used it to set the timezone in the controller on the only 2 actions where it was necessary.
def index
#user = current_user
#pending = #user.share_events.where("time > ?", DateTime.now.in_time_zone(#user.timezone))
#complete = #user.share_events.where("time <= ?", DateTime.now.in_time_zone(#user.timezone))
end
def new
#user = current_user
Time.zone = #user.timezone
#post = Post.find(params[:post_id])
#share_event = ShareEvent.new
end
I'm trying to display a count of impressions per day for the last 30 days in the specific users time zone. The trouble is that depending on the time zone, the counts are not always the same, and I'm having trouble reflecting that in a query.
For example, take two impressions that happen at 11:00pm in CDT (-5) on day one, and one impression that happens at 1:00am CDT. If you query using UTC (+0) you'll get all 3 impressions occurring on day two, instead of two the first day and one the second. Both CDT times land on the day two in UTC.
This is what I'm doing now, I know I must be missing something simple here:
start = 30.days.ago
finish = Time.now
# if the users time zone offset is less than 0 we need to make sure
# that we make it all the way to the newest data
if Time.now.in_time_zone(current_user.timezone) < 0
start += 1.day
finish += 1.day
end
(start.to_date...finish.to_date).map do |date|
# get the start of the day in the user's timezone in utc so we can properly
# query the database
day = date.to_time.in_time_zone(current_user.timezone).beginning_of_day.utc
[ (day.to_i * 1000), Impression.total_on(day) ]
end
Impressions model:
class Impression < ActiveRecord::Base
def self.total_on(day)
count(conditions: [ "created_at >= ? AND created_at < ?", day, day + 24.hours ])
end
end
I've been looking at other posts and it seems like I can let the database handle a lot of the heavy lifting for me, but I wasn't successful with using anything like AT TIME ZONE or INTERVAL.
What I have no seems really dirty, I know I must missing something obvious. Any help is appreciated.
Ok, with a little help from this awesome article I think I've figured it out. My problem stemmed from not knowing the difference between the system Ruby time methods and the time zone aware Rails methods. Once I set the correct time zone for the user using an around_filter like this I was able to use the built in Rails methods to simplify the code quite a bit:
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
around_filter :set_time_zone
def set_time_zone
if logged_in?
Time.use_zone(current_user.time_zone) { yield }
else
yield
end
end
end
# app/controllers/charts_controller.rb
start = 30.days.ago
finish = Time.current
(start.to_date...finish.to_date).map do |date|
# Rails method that uses Time.zone set in application_controller.rb
# It's then converted to the proper time in utc
time = date.beginning_of_day.utc
[ (time.to_i * 1000), Impression.total_on(time) ]
end
# app/models/impression.rb
class Impression < ActiveRecord::Base
def self.total_on(time)
# time.tomorrow returns the time 24 hours after the instance time. so it stays UTC
count(conditions: [ "created_at >= ? AND created_at < ?", time, time.tomorrow ])
end
end
There might be some more that I can do, but I'm feeling much better about this now.
Presuming the around_filter correctly works and sets the Time.zone in the block, you should be able to refactor your query into this:
class Impression < ActiveRecord::Base
def self.days_ago(n, zone = Time.zone)
Impression.where("created_at >= ?", n.days.ago.in_time_zone(zone))
end
end
I apologize in advance, this is going to be a long question.
Short version:
I have a Meeting model that has a date, start_time, and end_time. These are time objects, which of course are a pain for users to input, so I'm using virtual attributes to accept strings which are parsed by Chronic before save.
I have a plain vanilla rails controller that receives these virtual attributes from the form and passes them along to the model. Here is the controller:
def create
#meeting = #member.meetings.build(params[:meeting])
if #meeting.save
redirect_to member_meetings_path(#member), :notice => "Meeting Added"
else
render :new
end
end
def update
#meeting = #member.meetings.find(params[:id])
if #meeting.update_attributes(params[:meeting])
redirect_to member_meetings_path(#member), :notice => "Meeting Updated"
else
render :new
end
end
I've verified that the controller receives the correct parameters from the form, for instance params[:meeting][:date_string] is set as expected.
Problems:
On create, the date gets set correctly, but the times are assigned to the year 2000, set in UTC, and won't display in local time on the front end.
On update, the date won't update. The times update but stay in UTC for 2000-01-01.
Longer Version
What makes this super bizarre to me is I have decent test coverage indicating all of this works at the model layer.
Here is the model:
# DEPENDENCIES
require 'chronic'
class Meeting < ActiveRecord::Base
# MASS ASSIGNMENT PROTECTION
attr_accessible :name, :location, :description, :contact_id, :member_id, :time_zone,
:date, :start_time, :end_time, :date_string, :start_time_string, :end_time_string
# RELATIONSHIPS
belongs_to :member
belongs_to :contact
# CALLBACKS
before_save :parse_time
# Time IO Formatting
attr_writer :date_string, :start_time_string, :end_time_string
# Display time as string, year optional
def date_string(year=true)
if date
str = "%B %e"
str += ", %Y" if year
date.strftime(str).gsub(' ',' ')
else
""
end
end
# Display time as string, AM/PM optional
def start_time_string(meridian=true)
if start_time
str = "%l:%M"
str += " %p" if meridian
start_time.strftime(str).lstrip
else
""
end
end
# Display time as string, AM/PM optional
def end_time_string(meridian=true)
if end_time
str = "%l:%M"
str += " %p" if meridian
end_time.strftime(str).lstrip
else
""
end
end
# Display Date and Time for Front-End
def time
date.year == Date.today.year ? y = false : y = true
start_time.meridian != end_time.meridian ? m = true : m = false
[date_string(y),'; ',start_time_string(m),' - ',end_time_string].join
end
private
# Time Input Processing, called in `before_save`
def parse_time
set_time_zone
self.date ||= #date_string ? Chronic.parse(#date_string).to_date : Date.today
self.start_time = Chronic.parse #start_time_string, :now => self.date
self.end_time = Chronic.parse #end_time_string, :now => self.date
end
def set_time_zone
if time_zone
Time.zone = time_zone
elsif member && member.time_zone
Time.zone = member.time_zone
end
Chronic.time_class = Time.zone
end
end
Here is the spec. Note that to test the parse_time callback in isolation I'm calling #meeting.send(:parse_time) in these tests whenever I'm not actually creating or updating a record.
require "minitest_helper"
describe Meeting do
before do
#meeting = Meeting.new
end
describe "accepting dates in natural language" do
it "should recognize months and days" do
#meeting.date_string = 'December 17'
#meeting.send(:parse_time)
#meeting.date.must_equal Date.new(Time.now.year,12,17)
end
it "should assume a start time is today" do
#meeting.start_time_string = '1pm'
#meeting.send(:parse_time)
#meeting.start_time.must_equal Time.zone.local(Date.today.year,Date.today.month,Date.today.day, 13,0,0)
end
it "should assume an end time is today" do
#meeting.end_time_string = '3:30'
#meeting.send(:parse_time)
#meeting.end_time.must_equal Time.zone.local(Date.today.year,Date.today.month,Date.today.day, 15,30,0)
end
it "should set start time to the given date" do
#meeting.date = Date.new(Time.now.year,12,1)
#meeting.start_time_string = '4:30 pm'
#meeting.send(:parse_time)
#meeting.start_time.must_equal Time.zone.local(Time.now.year,12,1,16,30)
end
it "should set end time to the given date" do
#meeting.date = Date.new(Time.now.year,12,1)
#meeting.end_time_string = '6pm'
#meeting.send(:parse_time)
#meeting.end_time.must_equal Time.zone.local(Time.now.year,12,1,18,0)
end
end
describe "displaying time" do
before do
#meeting.date = Date.new(Date.today.year,12,1)
#meeting.start_time = Time.new(Date.today.year,12,1,16,30)
#meeting.end_time = Time.new(Date.today.year,12,1,18,0)
end
it "should print a friendly time" do
#meeting.time.must_equal "December 1; 4:30 - 6:00 PM"
end
end
describe "displaying if nil" do
it "should handle nil date" do
#meeting.date_string.must_equal ""
end
it "should handle nil start_time" do
#meeting.start_time_string.must_equal ""
end
it "should handle nil end_time" do
#meeting.end_time_string.must_equal ""
end
end
describe "time zones" do
before do
#meeting.assign_attributes(
time_zone: 'Central Time (US & Canada)',
date_string: "December 1, #{Time.now.year}",
start_time_string: "4:30 PM",
end_time_string: "6:00 PM"
)
#meeting.save
end
it "should set meeting start times in the given time zone" do
Time.zone = 'Central Time (US & Canada)'
#meeting.start_time.must_equal Time.zone.local(Time.now.year,12,1,16,30)
end
it "should set the correct UTC offset" do
#meeting.start_time.utc_offset.must_equal -(6*60*60)
end
after do
#meeting.destroy
end
end
describe "updating" do
before do
#m = Meeting.create(
time_zone: 'Central Time (US & Canada)',
date_string: "December 1, #{Time.now.year}",
start_time_string: "4:30 PM",
end_time_string: "6:00 PM"
)
#m.update_attributes start_time_string: '2pm', end_time_string: '3pm'
Time.zone = 'Central Time (US & Canada)'
end
it "should update start time via mass assignment" do
#m.start_time.must_equal Time.zone.local(Time.now.year,12,1,14,00)
end
it "should update end time via mass assignment" do
#m.end_time.must_equal Time.zone.local(Time.now.year,12,1,15,00)
end
after do
#m.destroy
end
end
end
I have even specifically mixed in creating and updating records via mass assignment in later test methods to ensure that those work as expected. All those tests pass.
I appreciate any insight into the following:
Why doesn't the date update in the controller#update action?
Why aren't times getting the year from the date that is set? This works in the model and in specs, but not when submitted via form through the controller.
Why don't times get set to the time zone that is passed in from the form? Again, these specs pass, what is wrong on the controller?
Why won't times display in their time zone on the front end?
Thanks for the help, I feel like I must be losing the forest for the trees on this one as I've been going at it for hours.
Update:
Thanks to the help of AJcodez, I saw some of the issues:
Was assigning date wrong, thanks AJ! Now using:
if #date_string.present?
self.date = Chronic.parse(#date_string).to_date
elsif self.date.nil?
self.date = Date.today
end
I was using Chronic correctly, my mistake was at the database layer! I set the fields in the database to time instead of datetime, which ruins everything. Lesson to anyone reading this: never ever use time as a database field (unless you understand exactly what it does and why you're using it instead of datetime).
Same problem as above, changing the fields to datetime fixed the problem.
The problem here has to do with accessing time in the model vs. the view. If I move these time formatting methods into a helper so they're called in the current request scope they will work correctly.
Thanks AJ! Your suggestions got me past my blind spot.
Well here goes..
1 . Why doesn't the date update in the controller#update action?
I see two potential issues. Looks like you're not parsing the dates again. Try this:
def update
#meeting = #member.meetings.find(params[:id])
#meeting.assign_attributes params[:meeting]
#meeting.send :parse_time
if #meeting.save
...
assign_attributes sets but doesnt save new values: http://apidock.com/rails/ActiveRecord/AttributeAssignment/assign_attributes
Also, in your parse_time method, you use this assignment: self.date ||= which will always set self.date back to itself if it is assigned. In other words you can't update the date unless its falsey.
2 . Why aren't times getting the year from the date that is set? This works in the model and in specs, but not when submitted via form through the controller.
No idea, looks like you are using Chronic#parse correctly.
3 . Why don't times get set to the time zone that is passed in from the form? Again, these specs pass, what is wrong on the controller?
Try debugging time_zone and make sure it is returning whats in params[:meeting][:time_zone]. Again it looks correct by Chronic.
Side note: if you pass an invalid string to Time#zone= it will blow up with an error. For instance Time.zone = 'utc' is all bad.
4 . Why won't times display in their time zone on the front end?
See Time#in_time_zone http://api.rubyonrails.org/classes/Time.html#method-i-in_time_zone and just explicitly name your time zone every time.
Not sure if you're already doing this, but try to explicitly save Times in UTC on the database, and then display them in local time.
I'm looking for a way to format date time in find(:all) so that when I render my results in JSON, the date time will look like
"March 20, 2011"
instead of
"2011-03-20T04:57:50Z"
Does anyone have any suggestion? Thanks.
OK, so you want to render the results in JSON formatted nicely. Instead of changing the format of the date on the way in, change it on the way out.
class Post
def formatted_created_at
created_at.strftime("%b %d, %Y")
end
def as_json(args={})
super(:methods=>:formatted_created_at, :except=>:date)
end
end
I would have used Date.parse(datestring) on the client to generate some usable content.
Time.now().strftime("%b %d, %Y)
Off the top of my head, you could do something like:
#posts = Post.all
#posts.all.each do |x|
x.date = x.date.strftime("%b %d, %Y")
end
#posts.to_json
That works (checked in Rails 3.1), put it into config/initializer/times_format.js. First two lines fix default time format (e.g. AR created_at). Third part is monkey patch for JSON.
Date::DATE_FORMATS[:default] = "%Y-%m-%d"
Time::DATE_FORMATS[:default] = "%Y-%m-%d %H:%M:%S"
class ActiveSupport::TimeWithZone
def as_json(options={})
strftime('%Y-%m-%d %H:%M:%S')
end
end
Look you use jbuilder? and for example index.json.jbuilder
json.array!(#textstrings) do |textstring|
json.extract! textstring, :id, :text
json.created_at textstring.created_at.to_formatted_s(:short)
json.url textstring_url(textstring, format: :json)
end
in this example I am use method .to_formatted_s
json.created_at textstring.created_at.to_formatted_s(:short
and i've got
[{"id":1,"text":"liveasda","created_at":"17 Nov 12:48","url":"http://localhost:5555/textstrings/1.json"},{"id":2,"text":"123","created_at":"17 Nov 14:26","url":"http://localhost:5555/textstrings/2.json"},
I have a form which i'd like to simplify. I'm recording a startdate and an enddate, but would like to show the user only a startdate and then a drop down with number of days.
But I'm having problems with my model and storing it correctly.
The first part works.
def date=(thedate)
#puts the startdate in the correct format...
self.startdate = Date.strptime(thedate, '%m/%d/%Y')
end
The problem I have has to do with the fact that the end date is based on the startdate + the no_days which is itself a virtual attribute. I tried doing the second part as a after_validation callback but it doesn't seem to work.
def set_dates
if self.startdate
self.enddate = self.startdate + days
end
end
First of all, why do you need to convert a date attribute in your startdate? Why don't you use something like f.date_select :startdate in you form?
Then, in your model you need something like attr_accessor :number_of_days with wich you can get the number_of_days as an integer in your form with f.select :number_of_days, (1..10).to_a (set the array as you like).
You can set your callback the following way:
after_validation :set_enddate
def set_enddate
if self.startdate
self.enddate = self.startdate + self.number_of_days.days
end
end